CA will do the job for 50 flights or so, but then, the planw will probably last for 30-40 flights without fuel proofing at all. I expect my models to last for 3-4000 flights, and generally they do.

I mask off and spraypaint the engine compartment with gray equipment primer ( a buck a can at your local hardware store). Then I sand lightly with 400 to knock off any rough edges. This step is not just to make it look pretty. Any stress fractures that develop in the engine compartment will show up clearly as white balsa streaks in the gray primer.

Next, I mix up a small batch of 15 minute epoxy. I thin it to the consistency of pancake syrup with DENATURED ALCHOHOL which is probably sold as Methyl Hydrate if you are in Australia. DO NOT use Isopropanol or "rubbing alcohol" from your druggist shop, as it will interfere with the cure of the epoxy.

Apply the thinned epoxy to your fire wall and the surrounding engine compartment using a good quality artist's brush. I use a 3/4" brush which allows me to do a very neat and clean job.

Clean up the brush with more denatured alcohol. If you are slow, and the epoxy starts to cure before you get the brush completely clean, use ACETONE to clean up the brush. Acetone, applied to a clean rag will also clean up any epoxy you accidently dripped onto the model. It will not attack most covering materials, but it will ruin peel and stick decals.

Care and attention to details like this are the difference between a model that survives for a season and a model that sparkles for years.