I cleaned mine the best I could with compresed air and a shop vac. If there was surface rust I hit it with the spray stuff that turns the rust black (I think its phoshporic acid, but don't quote me, I got the semi-cheap version from NAPA), then I stuck the nozzle of the spray gun in there and put paint in there like crazy. It was messy, but in the end it is probably the best thing I could do. I am sure it is better then the factory, and that held up for 41 years, so considering how little weather it sees, probably good.