Here is an old hotrodders trick that is relatively inexpensive and works well. Make up a solution of 1 part molasses to 5 parts of water and soak your mechanisms in that. There is an acid in molasses that will remove the rust, and not harm the good metal. I have known of guys who bought a childs plastic wading pool and mixed up large enough batches to clean the rust off of model A Ford fenders. It works slowly, (as in not too aggresive), but you don't want to dissolve the whole darn mechanism.