I used por-15, but mine was on a lift. Sand blasted bottom, then used the por-15 acid, then 2 coats of por-15 silver, then 2coats por-15 black. Note: por-15 is to go over bare or rusty steel only, not over undercoating.
Problem will be for doing it on jack stands, maybe. The acid treatment needs to be rinsed off, kind of making a mess if you don't have a floor drain.
In the pic, the surface is dusty from sitting in the body shop, otherwise it looks great. The por-15 is super glossy, so if putting something over the top of it will require it to be scuffed with a 3M pad.