That grinder spins at what, 10,000 rpm?
The only thing I have found that will hold up at that speed and cut both paint and rust is a braided wire cup brush. Straight-bristle wire brushes will fly apart and leave you picking wires out of your legs and arms. Most sanding disks are not balanced for high speed, and will buck and gouge or become shrapnel. If you use a braided wire cup, you must keep moving or it will scorch and warp the steel quickly.
