X2, Why Imron, are you trying to match body color? Do you have a bunch of extra or something? What look and color are you trying to end up with? I am assuming if you are even thinking of brushing it on, looks are not a big concern. I would spray it, not use a brush. Since it is on the underside, you can get some Industrial Machine urethane a lot cheaper than car paint and way more durable. Sherwin Williams makes Polane which is super tough. The main drawback is that it does not have the UV protectors in it that car paint does... but for the underside, it is not sitting there baking in the sun anyway.
