A couple of other options for fuel proofing:

1. Thin the epoxy with acetone (about 10% by volume ). It will take several days to dry though.

2. Use clear fuel proof dope (Aerogloss or similar ).

FWIW - I normally use thinned epoxy on the firewall and in the fuel tank compartment. Any other exposed areas I use clear dope (push rod exits, aileron hatchs, etc. )