What is the proper amount of coats of POR 15 to use. I have done 2 so far and looks pretty good, but is this enough. I am brushing on.

I think two is good enough but i think you can always apply another, don't take my word, call the POR tech, go to there site. Good Luck

Where are you painting?

Here is what I like to do for the sides of the frame and inside the trunk.

On the inside floor, 1 coat.

A coat of sliver (fills minor pits better, but does not cover as much), 2nd coat of black. easier to see where you have been. I used flat instead of semi.

On rears, and other down-side suspension parts I just do 1 quick coat. Stay away from bolts or threaded areas! Get close then use some krylon to get it on it.