you can get soda blast media, glass beads and walnut shell media at Harbor freight tools. I used duponts star blast on my boot deck, the under side, after I had all but finished the body work on the out side, thought I took it easy but still warped the flat pannel, I wouldnt use sand, soda blasting would be the best not to warp it, put down a big blue tarp, if you can hang the tarp up against a wall and do the blasting there you can reclaim the media many times, but each time you will have less. thats if you dont have a blasting cabnet
Hondo