If you thin Ambroid glue with acetone, you can brush it on the firewall and engine compartment for a fuel proofing that 's hard to beat. Not as messy as using epoxy and looks good too. I've used Ambroid since I was a kid in the 50's and still use it today. You can order it from the manufacture in quarts, and gallons.
I have found that I can thin it with acetone and use a brush to paint my wood for bonding. The thinning seems to help it soak into the wood and provide a much stronger bond. It dries fast, is fuel proof and easy to sand.

I don't think the formula has changed at all. It is also available at my local Hobbytown USA hobby shop.

Frank