I did attent the PrepExcellence school, and I highly reccomend it
I have two additional thoughts...
High speed? I almost always run on the slowest speed, and allow the product to do the work.
Get a damaged hood or trunk from a local body shop. introduce a variety of scratches, and then see if you can remove them... try to burn a section. See how long it takes...
Buy an infared thermometer at radio shack, and never let the surface temp get above 115 degrees.
OK, that's 3...
Good Luck!
Jiim