Newman Atkinson says:

Gary, To remove the paint might be as easy as putting the parts in a container of Concentrated Simple Green. It works well with plastic train cars without hurting the plastic. I am not sure if it would harm the metal. As far as the rust How ever you decide to remove the paint, use some rust inhibitor maybe something like lock ease lubricant.Buff it with the lubricant You will have to clean it good before repainting I am sure. One thing for sure is if you just remove the rust without removing the paint it will most likely look like you the good paint stuck out from the metal when painting over it if the old paint is not remover also. Using wire brushes most likely will scratch the metal and it will most likely show with the new paint. Might try a dish washing scrub pad with a buffing wheel such as an orbiting sander and the lock ease type oil. Just some suggestions here from Newman

David A Stokes says:

If rust is the issue then I presume we’re talking tinplate. The vintage car brigade submerge their rusty bits and pieces in a molasses solution. A gallon to 5 gallons of water, well stirred. Leave your items in the solution, but check progress at least daily as it can work really fast, or take weeks depending on the paint. Molasses can be pretty harsh so take care.

John Michael says:

To remove rust, try Evapo Rust, available at Harbor Freight, Lowes, Home Depot, Wally World. Used by the military to remove rust from M1 Abrams tanks, they actually have a vat they drive the tanks in!
I have used it on delicate precision instruments without harm, works great, use it on tools, etc. and no I have no affiliation with the manufacturer.