I have one of those heat guns, the kind you use for stripping paint. I use that after I have cleaned things like the bolt and breech plugs on my knights. They will dry out right now. Then I put some protective oil like breakfree on them. I have never used the heat gun on the barrel because I always rinse it with very hot water. I would think a person could dry areas around the thimbles if you are worried about moisture in those cracks. You have to be careful around rubber gaskets or plastic parts.
Art