just a note on that advice... its very good and technically correct.. your advised to put a sealer primer over your initial epoxy primer, BUT it isn't absolutely nescesary... most will just throw 3, 4 coats of a good high-build epoxy primer on, sand with 320, 400 and paint.. saves ya a couple steps...
an important rule of bodywork is, tho you can hide, fill, etc imperfections with the following coats, you generally want your primer thoroughly sanded and perfect. no orange peel, dings, deep scratchs, etc.. they will transfer thru to your next coat... " your paint is only as good as whats underneath"...