Dave,
Thinned epoxy is the most chemical or fuel resistant coating , followed by solvent based polyureyhane and then clear butyrate dope. Although butyrate dope is touted to be fuel proof, raw soaking glo fuel will damage and remove it. Stay away from any water based coatings.
The easiest way to go is clear Min Wax solvent or oil based polyurethane. Comes in small half pint cans at most paint or hardware stores.
I prefere epoxy thinned with denatured alcohol but the preparation does require a little more work.
BTW if your tank and tubing is leak checked prior to installation there is no need to fuel proof the entire tank compartment. Just everything forward of the firewall and maybe the back of the firewall.