Yeah, how do you guys design for that? I'm having trouble even making basic shapes.
Practice, practice, practice! There really isn't a shortcut, you just have to keep at it.
That and I find that sketching out your designs helps a lot to figure out various unknowns before modelling the case.
Today, I played CLUE with a few friends, setup the nine out of twelve usable buttons on my Huion New 1060PLUS, and now I am about the do some sketching in Krita.