I need to do the Fowler thing and I notice that the NACA reports show the retracted and the fully deployed configurations, so my question is: What should happen in between?

I can make the flaps slide backward most of the way before rotating... but that forces them to slide down and out parallel to the wing UPPER surface and jut into the airflow below.

I can make them rotate evenly throughout their travel... which is what I know a lot of models do, but that makes them fairly draggy, even at fairly low deflection angles, so I wouldn't get maximum bennefit for takeoffs.

I can make them rotate just a little as they slide backward and then rotate at a much higher rate once they're back... seems like the most practical thing to me.

Any insight on how "the big boys" do this, or how you've always done it, or how's a bad way I should avoid, or a textbook right way, or ....?