It is fairly simple once you get the hang of it. You start to get a "feel" for how one overly/pose will effect another. And of course they have a diminishing effect as well. The more you have stacked on one sim the less effect they will have. I use that to my advantage a lot. Like with the Purse 6 pose in this example. If there had only been one other overlay at work on that arm it would have brought his whole arm down almost up against his side, rotated his hand over so it was palm up and just about completely closed his fist. Except because of the other overlays at work it was only a very slight rotation of his hand and a bit of a drop in his elbow.

I hope that made sense ...

But, yes! Do try it.