There was just a thread a few weeks ago on this and I can't find it. But you most certainly do NOT want to cool the weld! Cooling hot metal is how you SHRINK it, you do NOT want to shrink the metal after every weld!
I'm sorry to be rude Al but I don't want someone go read your post and walk out and start welding and cooling.
Keeping the metal cool, lightly cooling it, yeah you can do that with control but you do not simply cool the hot metal after welding with a wet rag, others may not understand what you meant. It WILL warp the metal, it is shrinking after all.
I personally weld 1/4 inch welds with a lot of space in between, we are talking a number of feet. I would take days, many days to weld that up. Letting it cool between each weld on it's own, we are talking until it is totally cooled.
I'll try to find that thread.