I have the bottom of the line skimmer, the one without the overflow thingy. They seem very simple and I like the way it sets up and runs. The only time I have to adjust mine is when I dump my cup. I just turn the flow pretty much off, dump the cup & replace, then turn back up to where flow knob used to be. I keep an eye on the foam to make sure it foams to where it needs to be just in case.
You got the idea. You want the foam to occasionally rise to where the cup starts to "cone in". You don't want the foam to constantly be at the "cone in" or above. The idea is to have the flow just so.....so that your foam is at a level just above where cup connects to the main skimmer body. I've noticed this level seems to be optimal for skimming. Just check your cup frequently, if it slowly fills with thick brown stuff, it's working as it should. If it fills with clear or translucent stuff, turn the flow down.