I use Probond/ Gorilla glue instead of epoxy in most cases anymore, it has proved to be stronger than epoxy in my applications. Thin CA glue works great for fuelproofing, also use aerogloss dope and brush it on in layers until it looks solid and uniform (after covering is aplied to fuselage, helps seal edges near the firewall area). I've had great success with balsarite as a fuelproof coating also.