Best way to clean the internals of a Redhawk cylinder?

the Redhawk cylinder and crane, don't take it apart. Couple of small parts that can easily be lost. If it is not spinning freely it is the ejector rod running thru the cylinder that is gunked up. You might try holding the gun over a trash can and spraying Birchwood Casey Gun Scrubber into the face of the cylinder with the ejector rod pushed out like you are ejecting brass. Some of the spray will go down into the center of the cylinder and that should help a bit. The best thing would be if you know a good gunsmith that is familiar with the Redhawk have him take the cylinder and crane apart and spray out all the internals. Oil gets inside the crane and cylinder and eventually turns hard and keeps the cylinder from spinning freely. It also attracts sand, dust and grit that is around it or in a holster with it and that hurts it also. That is why I always am harping about keeping oil out and away from all guns. Oil is the worse thing you can put on a gun.
Anyway having the crane and cylinder taken apart and degreased it is the only real way to take care of the problem.

soak it in a solvent and blow it out with compressed air, use a can of brake cleaner, buy an expensive can of name brand gun cleaner, etc etc. Or just soak and let it drain. If playing with compressed air or canned products, make sure eyes are protected.