Howdy back Steve-o and All:
To adjust the low speed air screw 1st know that to turn in in leans out the idle mixture. Lean means that it will run hotter. turning the screw out richens and cools. The low speed air screw also helps with transition to mid range.
If the carb is stock/OEM the factory trys to have the setting close with 1 1/2 turns out from a gentle stop. This is a good generality, but not an absolute. If you have a good vacuum guage hook it into a full maniflod vacuum source. With the engine running and warmed up to operating temp- no choke and no fast idle, set the idle speed. Now turn in the idle air screw until the engine begins to lose rpms. Now turn the screw out until you hear the highest rpm. Watch the vacuum guage needle for it's highest mark. That is the ideal idle setting for a stock engine with a stock carb. If you keep backing the screw out the vacuum will not increase. Now slowly turn the screw in until the needle just begins to drop, back it out to the setting just prior to that drop. Readjust the idle speed.
If you don't have a vacuum guage, listen for changes in rpm. As you back the screw out from the stumble the idle speed should go up. If this isn't working, consider that something else is wrong.
This should give you the ideal idle setting for a stock engine with a stock carb. It may not be ideal for a modified engine and/or a non-stock carb. driving and trying other setting may improve on it.
If you continue to back out the air screw past the ideal setting you may still be richening the idle mixture, which should produce a cooler engine at idle, and help with transitions from idle. How much? It depends. Try it and see.
Adios, David