this is a very good point on the d.a i have help may here. running the d.a to dam fast the sandpaper lose it grit and makes heat and if you pay for the paper you try to make it last . i fixed a 64 gto hood that was a geat hood till some shi$t head fixed it by d.a it look like he was standing on it when he strip it with a d.a. grinding d.a and disc sander 36 grit and griders should be band from some . this suff in the wrong hands can make it hard to do a good job and griding hi spot thats a big NO NO i did all my metal work with a hammer and dolly and a slap file then i guide coat it and work it till it look good it is better to take off the guide coat and work the metal more than grinding the crap out off it and when it is rigth as you can get it before i use filler