I agree with Phlip. A few months ago in Model Airplane News, Dawn Power Dissolver was reviewed. A member of a local club tried it and said it works great and was quick and easy.

I have not tried it so I am only repeating what I heard. He said all he did was spray it on, wait a little bit, then brushed the engine with an old toothbrush and the varnish came right off. He tested it on a 20+ year old Fox .35 engine and the picture he showed makes the engine look like new - all bright and shiny. No long wait, no taking the engine apart, no dangerous fumes, etc.

I think I would rather do that than the crockpot/antifreeze method, but I'm basically lazy...