HiZ, I am sure the pro's could give you some better info, but......
When I did my boat, I had removed carpet and the adhesive it left behind. The transom and "bilge" area under the motor were painted grey. I used greased lightning and srubbed down the entire area. After doing that, I used Acetone to remove all of the adhesive. I then lightly sanded the entire area and wiped it down with Brushing Liquid, primed with Interlux Pre-Cote, lightly sanded again, wiped it down with Brushing Liquid, then painted with Bligekote. (2 coats)