Spray-bomb it with Rustoleum of Krylon. Depending on the color of your car you may even be able to get fairly close to the exterior color. I've done this a few times ... I always super clean the underside first, remove any rust scale, paint the frame with semi-gloss (you can unbolt the brake/fuel lines and cover with tape), then wrap the frame with newspaper and tape, wrap the driveshaft and exhaust and spray the floor pans. Be sure to thoroughly cover the car with plastic drop cloth or some type of cover as the the paint dust always finds a way to sneak into unprotected areas. If some overspray gets onto anything make sure to clean with rubbing compound or other products ASAP before it sets up. The longer it sits the harder it gets to remove.
You can use spray undercoating, but the look of body color paint is better in my opinion. The factory hit the floorpans with body color, but not a thorough covering.
Good luck.
|