Here is a recipe for home made "Waxoyl". It's an old fashioned rust treatment / undercoating: 2 1/2 quarts turpentine 12 oz. beeswax / candle wax 1 quart light machine oil With a cheese shredder, cut the wax into the turpentine, stir until the wax has dissolved, (takes a long time; you can use very low heat (a warm room) to aid but be careful) and thin with the machine oil to a brushable / sprayable consistency. Apply liberally. You can use a hand spray bottle to get into closed-off sections if you have a small access hole. Please be sensible when you make this stuff; don't go breathing the fumes or applying heat and burning down your house. If you have any doubts about it, err on the side of caution and just buy a commercially available product.