The trick is to take off excess weld without thinning out the surrounding sheet metal. Its a pain in the keester, but for best results use a 3" x 1/16" cut off wheel in an air grinder. Grind at 90 degrees to the weld bead with the edge of the wheel. This takes two hands to maintain control, but it is very effective to knock down the bead without thinning out the metal. When the majority of the bead is removed, then a disc made of overlapping flaps of paper (I don't know what they are called) is good for the finishing touches and to blend everything.