Dr. Marneaus
Station Wagoneer
Where the waggy rusts, I'm not sure you could get anything sprayed in there, because it's between the inner and outer panel. Might be able to do it with the long nozzle used from something like the inner frame rail paint from Eastwood. Not sure how to get between the floor board panels but the fender wells may be easier.
When I redo the fenders on Flip I plan to do some drainage holes, and spray up inside with a sealer, so the next person won't have to worry so much.
Why add drain holes when nature already added, or will add them given the time, them for us!?