Yeah, I think the thing is to see if you can possibly draw from the arm not the hand. Maybe you should do a couple oil pastels real big from magazine photos or whatever and see how it feels. People paint with expresso coffee with a brush (you can mix strong instant coffee) or charcoal sticks soaked in linseed oil too... materials that permit big painting  without big expense. Right now I am using good quality (Prang) children's poster paints on paper cut from a huge roll of butchers paper and craft paper... I have also used rolls of freezer paper. The thing might be to find a new way of working, big gestural drawing or torn paper colages or something. I have an old text book called "Art for Spastics" which was intended for special education teachers working with people who had CP (Cerebreal Palsey... did I spell that right?) and it has interesting aproaches to art making in the case of motor difficulties... maybe you could find a book like that or something on-line. I miss my old c.1998 drawing software (I can't afford a Mac to run it now) that allowed me to draw fluidly despite Parkinsonism through patern recognition and intelegent tremor suppression... closest I have found is drawing in Flash but I can't afford flash and the workspace is confusing to me anyway.