Set welder heat to provide full penetration weld dot. Planish the weld dots, use a 3" cutoff wheel to grind down the weld dots to just above panel surface, then overlap in making the next welds.
If your welder is set to provide full penetration welds on 18ish gauge metal, leaving weld dots there without grinding and trying to weld on top of weld is the same as increasing panel thickness anywhere from 3 to 5x the thickness. Essentially, you are setting yourself up for cold welds. Weld, planish, grind, repeat
