Step 2: remove the paint. I am using a 4" knotted wire cup on a grinder, and wore a respirator and eye protection. Word to the wise - eye protection is a must. The knotted wire cup is an aggressive approach, but it gets through the paint, roughs up the metal, and doesn't dig into the metal as long as you keep the grinder moving. For these older vehicles with thinker panels, I highly recommend this method