Wow, that was so long ago. I only remember that it was white paint with some slight texture. It was made to paint boat decks to keep you from slipping, I think. It was probably oil based, but I'm not sure. (That was in the early 80's).
RE: the frame - I built the basic sink frame from plywood, then places support pieces (1x1's, I think) along the bottom in a way that would create a slight slop when the plywood sink bottom was laid down on them. Once that was all put together, I drilled out a drain hole, then did the fiberglass cloth and resin thing.
I think that book I mentioned is still available, and there's probably an updated edition. I used the marine paint both to add some waterproofing (just in case) and to make it a nice white. I kept it clean and it never stained on me.