Our Service Dogs receive six to twelve months of training, including several months of training to your specific needs and circumstances (this last period depends on how extensive your needs are).
At Pawsitivity, we use the same method that both the U.S. Army working dog program and Guide Dogs for the Blind uses:
"All of the dog training is based on positive reward or feedback" -- U.S. Army Training and Doctrine Command.
Because of its effectiveness, “training procedures are similar for all types of service dogs. Trainers use positive reinforcement techniques" (emphasis ours).
Why Do We Train This Way?
As Pawsitivity learned (in our 2017 Positive Training workshop in Portland, Oregon), Guide Dogs for the Blind, the largest guide dog school in the United States, used to train with the old-school aversive methods, but upon switching to modern positive-reinforcement methods they not only increased their pass rate, but also, "the dogs can become full-fledged Guide Dogs in half the time." The Canine Department of the Netherlands National Police Agency reported, “[With] the first dog, [it] took me eight months to train him to follow a laser. With operant conditioning, it now takes me four weeks.” 
Fewer side effects
One of the big advantages to using positive reinforcement is that there isn’t the same risk of side effects. Simply put, "animals become afraid, either of people in general or of specific individuals as a result of aversive handling". Not only does the dog find this kind of training unpleasant, but the use of aversives also can damage the handler's relationship with the dog. Most dogs will sell their soul for a tiny bit of hotdog (or, for high-drive dogs trained for police work, a rousing game of ball throwing). We can also use praise, and we can build in real-life rewards, such as getting to walk through a door. The dog doesn’t just get to run through—by sitting and waiting for the release word, the dog gets rewarded by getting to go outside for a walk. Or when out for a walk, the dog is rewarded by getting to cross the street after sitting. There's many ways a handler can reward a dog for doing what you want him to do, which also helps to keep up his training. The dog doesn’t know it’s work—it feels like a game. This way, both the dog and handler win. A 2014 study in the Journal of Veterinary Medicine concluded that side effects (aggression) often occurred when dogs were taught using aversives. Thus, “There is no consistent benefit to be gained from e-collar training but greater welfare concerns compared with positive reward based training.” A 2013 study published in Applied Animal Behaviour Science found that owners who used methods based on positive punishment and negative reinforcement were more likely to report their dog was aggressive toward family members or strangers outside.
Less stressful for the dog.
Another study from Applied Animal Behaviour Science looked at two classes of dogs being trained to sit. One group lured its dogs into a sitting position with a treat, and the other group pushed down on its dogs’ behinds to force them into position. The study showed that with positive reinforcement, the dogs were 15 times less likely to cower or slink away from their owner. Additionally, the dogs trained with positive reinforcement were more likely to look their owner in the eye. Because we want to encourage a service dog to look at his/her handler and to initiate social interactions, this study’s conclusions dramatically demonstrate how much richer the handler/dog relationship can be with positive reinforcement. Positive-reinforcement training is also much safer (and presumably less stressful) for the handler and their family, as well.
Dogs will offer behaviors
Another advantage of positive reinforcement shows itself in that a service dog trained this way will offer lots of behaviors. With use of adversities, one runs the risk of the dog “offering fewer and fewer behaviors” because “not behaving is not the same from the dog’s perspective as exhibiting improved behavior.” In other words, if a dog doesn't fear punishment for doing the wrong thing, the dog will feel free to try various approaches to getting rewarded until the dog finds the right one.
 Military Working Dogs: Guardians of the Night, Linda Crippen TRADOC, May 23, 2011, U.S. Army, https://www.army.mil/article/56965/Military_Working_Dogs__Guardians_of_the_Night.
 Hand, Carol. Cool Careers Without College for People Who Love Animals. New York: Rosen, 2014.
 Coren, Stanley. How Dogs Think: Understanding the Canine Mind. New York: Free Press, 2004.
 From a three-year project for the Canine Department of the Netherlands National Police Agency, 1996, Simon Prins, coauthor of K9 Behavior Basics: A Manual for Proven Success in Operational Service Dog Training (2010).
 Adams, G.J., and K.G. Johnson. "Sleep, work, and the effects of shift work in drug detection dogs Canis familiaris." Applied Animal Behaviour Science 41 (1994): 115-126.
 Guide Dog News, the Quarterly Publication of the Guide Dogs for the Blind 59, no. 2 (2009).
 Cooper, Jonathan J., Nina Cracknell, Jessica Hardiman, Hannah Wright, and Daniel Mills. “The welfare consequences and efficacy of training pet dogs with remote electronic training collars in comparison to reward based training.” PPLoS ONE 9, no. 9 (2014): e102722.
 Casey, Rachel A., Bethany Loftus, Christine Bolster, Gemma Richards, and Emily J. Blackwell. "Human directed aggression in domestic dogs (Canis familiaris): Occurrence in different contexts and risk factors." Applied Animal Behaviour Science 152 (2014): 52-63.
 Deldalle, Stéphanie, Florence Gaunet. “Effects of two training methods on stress-related behaviors of the dog (Canis familiaris) and on the dog-owner relationship.” Journal of Veterinary Behavior 9, no. 2 (2014): 58-65.
 Herron, Meghan E., Frances S. Shofer, and Ilana R. Reisner. "Survey of the use and outcome of confrontational and non-confrontational training methods in client-owned dogs showing undesired behaviors." Applied Animal Behaviour Science 117, no. 1-2 (2009): 47-54.
 Rushen, Jeffrey, Allison A. Taylor, and Anne Marie de Passillé. "Domestic animals' fear of humans and its effect on their welfare." Applied Animal Behaviour Science 65, no. 3 (1999): 285-303.
 Shaw, Julie K., and Debbie Martin, eds. Canine and Feline Behavior for Veterinary Technicians and Nurses. Ames, IA: Wiley, 2015.
 Mech, DL. “Whatever happened to the term “Alpha Wolf?” International Wolf 18, no. 4 (2008): 4-8.
 Appleby, David. The APBC Book of Companion Animal Behaviour. London: Souvenir, 2010.
 Overall, Karen L. Manual of Clinical Behavioral Medicine for Dogs and Cats. St. Louis, MO: Elsevier, 2013.