i dont know how serious you would want to get, but im sure a community college near you offers some cheap auto body courses where you could learn and practice the "right" way to do things... probably not too expensive...
if you are intent on doing this online try searching google a bit with things like "auto body and painting how-to" .. i searched real quick and got this hit
http://www.autobody101.com/ . it actually seems pretty informative and theres a downloadable manual on how to paint there.