I found an old thread about leaning out a rich O/L idle, and the person said that LOWERING the IAC counts (IAC vs Temp) will lean things out. I was under the impression that lowering the counts meant that the IAC was opening less and richening the mixture.

What is the correct method? Higher counts = righer AFR or lower counts = richer AFR.

I've tried lowering the counts significantly and have yet to see any improvement in the clouds of black smoke coming out of the exhaust.

 

Well, IAC isn't supposed to directly affect AFR. I see in your other post that you're changing the O/L AFR stuff, which is probably more where you want to be. Black clouds are REALLLLLY rich. Like nearly DOUBLE the correct amount of fuel.
IAC counts is only to help the ECU know where it kind of should be in order to keep the idle speed correct.