Why would you want to take it to bare metal? Factory paint is the best primer. If it has been painted one or more times just take those coats off.
If you have to take it to bare metal I would use a variable speed large grinder, with an 8" foam pad, self stick 36 grit paper. Then use 80, then 180 paper on a 5" or 6" DA. Use Aircraft Stripper to get in the hard spots, and also for the large areas that the 36 grit might heat up and warp.