Can't help with finding a trainer but my advice (which someone gave me) was just go for it, its not as hard or daunting as you may think. I'm sure there are many ways of doing it but I found dispatching them with an air rifle was the best way, have someone else secure the bird, nice and relaxed then a quick pellet at point blank range stuns and bleeds the bird fairly quickly. A quick hose down then a dunk in a pot of hot water for 40 seconds makes plucky a doddle. Just take your time dressing them, as long as you don't contaminate anything with stomach or gut content it doesn't really matter how you dress them. I start at the neck, open it up and take the gizzard out. Go to the other end, hold the bird up by the legs and give it a shake to move everything away inside to reduce the chance of cutting anything when you're opening it up. Cut around the anus then pull it out followed by the intestines etc, then cut round the diaphragm then carefully reach in and pull everything else out. Its not a pleasant job but its quite rewarding when you have your nice homegrown chicken sitting ready to go in the oven. The main thing is to keep everything nice and clean and ensure no contamination gets to the meat. It gets easier with every bird you do.
Good luck!