Use a cheap water based polyurethane to seal the inside of your cages before applying any sort of epoxy resin. This will prevent the wood from soaking up the resin and will allow you to get away with one coat. Especially when applying it to oak which is very textured and grainy.
More on resins, epoxies, etc.:
After I posted I became curious and decided to shop around on the net to see how much fiberglass resin costs. I generally found about $9 to $12 per quart. Since it is not a two part system that is about $36 to $48 per gallon.
I guess that's not as cheap as I thought. The Envirotex Epoxy I use is about $50 per gallon. It has no fumes. You could even use right inside your reptile room safely.
It's much easier to work with than fiberglass and well worth the extra few bucks per gallon.
>> I have contemplated using it in a monitor enclosure next.
This is one place where I believe fiberglass resin is useful due to it's excellent scratch resistance. I love the Envirotex but I'm not sure it would hold up to scratching.
I've heard the West Systems Marine Epoxy is about as easy to use as the Envirotex and does not have bad fumes. I believe it's more expensive, though. Worth looking into if you're out of fiberglass resin and want to try something else.
Here's a cage I sealed with Envirotex. I can't begin to tell you how much easier it is to use than fiberglass resin. It would be great for GTP's, I'm not so sure about monitors.
This cage houses Uroplatus geckos and has had wet sphagnum moss on the bottom for about a year and a half. Even when you remove the wet sphagnum the epoxy is still as clear as what you see on the sides and back of this cage. Excuse the picture. This one was taken during it's setup.
Great product.

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Current snakes:
1.1 Gonyosoma oxycephala - (Silver/Yellow)
3.4 Gonyosoma oxycephala - (Green)
2.1 Gonyosoma janseni - (Black)