need tips on painting engine

Like anything, prep is the key. The cleaner you get the motor, the longer the paint will last.
I spray brake cleaner on the assembled motor, as final prep. Let it air dry, before painting.
The factory "did not" primer the engine. I suppose it was not cost effective. Im sure a nice coat of epoxy primer wouldnt hurt, but I just use paint. I use Mopar Performance paint in a rattle can, and have never had a problem with it. Again, prep is key.