Hope this helps ya, well at least this is what I do.
I sand the seams with 800grt sandpaper, then white primer coat...can be white Createx.
After the initial paint scheme I then shoot a coat of Createx Clear Coat. The reason I do this is because if I mess up on an eye, a gill, shad spot...whatever, I can easily wipe it off without messing up the initial paint scheme. I've had to start over many many times on an other wise great paint job because I didn't know about the "clear coat".
Then after the clear coat I add the eye's, gills, shad spot....what ever. Then top coat with Devcon 2 Ton epoxy you can find at Wall-Mart for $1.97 a tube.
I also help things along with a hair drier on the paint and the clear coat....not the Epoxy.