There are lots of good companies out there. Tantrick as has been mentioned, then there is Couture, Sun Junkie, and my personal favourite Vani-T. Do get some samples first to try out and decide for yourself.
As Scatty said though training can differ enormously (my training lasted 20 minutes). I think though that this has made me a better spray tan tech in a funny sort of way because I had to learn myself how my minimist came apart for cleaning etc, but for spray tanning advice it is a good job I have a daughter who had previously trained and was able to give me further advice.