I've used quite a bit of the Eastwood stuff. Drill holes behind the skid plate to let it drain correctly. Give it a few days to dry, and tape all the holes. It should take 2-3 cans. Be sure to spray inside the crossmember above the gas tank. Water lays in there too.
I used 2-3 cans per side. I mistakenly used Fluid Film a couple of years later. Mistake IMO, because you can't recoat the Eastwood and have it stick once that greasy crap is inside the frame.