<p>At the moment, I am thinking about print fans that cool the plastic when printing. I am not asking about the design of the fanducts, which might be a whole book on its own. I would like to know how to find out the best application of print cooling for a given PLA filament, - that is fan speeds and setup in a slicer of your choice (to learn what the different options are).</p>

I use side-wind to cool down model as simple as possible. It's just a 12cm in diam fan which is driven from arduino (the same contacts as the fan next to the nozzle). No duct, no other stuff. The only thing I consider in terms of making things better is to set up 2 fans which could coll down model from both sides.
The issue is that when model is more complex then cool air is not reaching out oll these crannies and then on some corners I see the difference. Because of this issue I have to orient model facing to the fan in the way which will decrease such effect and I'm usually happy with results. If you are able to imagine how the airflow behaves then you can achieve perfection :)
Of course fan is driven but to be honest I usually use 100% of its blowing power except with first layer which I usually don't blow at all.