Unfortunately, there's no magical way of getting moisture out of wood behind a wall of glass other than the solution that you already know. Exposing it to the air. Many people just live with the small dark spots that show that moisture has penetrated the skin (once they fix or recoat the area)

You could drill some small holes in the area, and let it dry or help it along with a hair dryer. You cold thin some epoxy with alcochol and let it get absorbed into the wood too. That's all that the dry rot stuff they sell in boating stores really is. Even on their bottles, they recommend having the area dry.

Be cautious with applying too much heat. Heat will soften the epoxy and in some cases make the weave of the glass suddenly appear. I don't know what happens, but I made this mistake once and the glass fibers suddenly were no longer transparent. I was using a propane torch.

If the area is on the inside and easily reachable, you're in luck becuse there you could cut a way some glass and drill some small holes to dry it out and re-glass a patch.

If it's only accessable from the outside and a big noticable dark area you may have to go into surgery and cut away some glass. Dry it out and re- patch it.

good luck - there's no easy way of getting the moisture out.