Body Work Tutorial

Have any of you used a DTM (direct to metal) 2K instead of an epoxy or etch as a base primer ?

Maybe someone can run through the different types of primers and were and when you use them ?

Epoxy primer
Polyester primer
urethane primer
high build 2K primer
Lacquer primer

Theres so many choices that it can get real confusing especially forr someone like myself who spent about 2 years in a body shop knows enough to get myself in trouble lol