[nikwho]

I have used the phosphoric acid in a spray bottle before, but it's not friendly to the lungs. I normally just pour some in a small cup and paint it on. Any time I go get some of this stuff from H.D. I always grab a big handfull of their $1 cheapo paint brushes from the painting department. That's how I did my '67 Pontiac. When I got it, the entire body was covered in superficial surface rust. I would paint on, leave for 10-15 minites, then wipe off and repeat. You CAN wipe it on, then leave it as in convert's the rust to an inert substance, but I don't like leaving it. The converted rust will eventually start running and dripping off of the metal. I repeat this until I'm down to shiny clean metal!