Once all th underside is nicely painted and looking good, it seems a shame to black under seal it. What's generally done?
You can get waxoil in clear I used black as the underside of my bus is black. Sent from my SM-G960F using Tapatalk
Avenue Coatings in Slough is the place to go. They have an ebay shop as tools_paint or tools-paint. Rustoleum is top class paint and easy to apply with brush or roller, can be thinned a little with white spirit. In my van today with Rustoleum L90D painting the panels behind the old units I took out last week. The finish is very pleasing, now I am thinking of doing the whole interior while I have access.
I wouldn't spoil a nice paint finish with waxoyl plastered over it. A paint finish is easy to keep clean and easy to spot any rust areas.