need help for BP / pad combo

Ok i have an inexpensive rotart ans a w65 backing plate i helieve its 6.25 inches, i have never used it and plan on using it to work on a buddys heavily oxidized suv, he dosent care about it so im not too concerned about burning or ruining it as its already trashed, i know i will need heavy cutting and i plan on getting pratice hood before trying on his car but what pads are good for rotary... i have a flex 3401 and a PC but dont think they will handle the job, i wont have pics until monday but ahy ideas?