If you're interested in offering this service, then the best promotion is probably to advertise that people with disabilities will be accepted with respect, communication, imagination and passion.
As for training and education, I can recommend the book "The Ultimate Guide to Sex and Disability". It's available at online booksellers, and I believe locally at Venus Envy (http://venusenvy.ca/ultimate-guide-sex-and-disability). Venus Envy also regularly runs a sex and disability workshop (http://venusenvy.ca/events/everybodys-doing-it-talking-about-sex-and-disability-2013-03-26), although I have never attended, so can't comment on it.
I'm not an expert in disability other than my own (incomplete spinal cord injury), but can tell you that there's a broad range of issues and some challenges to overcome. Mobility disabilities may require out-calls, positioning assistance - sometimes devices, sometimes lifting by yourself or an attendant. Your tantra chair would certainly be one form of assistive device for CPs, paras and quads that transfer themselves. Overcoming these sorts of challenges is where the imagination comes in.
As with the able-bodied, things work better when take your time, ask questions about what works for them, and encourage frank communication! :-)
