EnduroExpertFSR- You *can* use the edge of the pad with a PC, just use a little common sense and you'll be fine. When I need to get into spots like those you mentioned, I generally use a *larger* pad, not a smaller one. I'll force/deform the pad into the area in question, or use the edge of the pad, or the section that overhangs from the body of the machine. With some styles of pads you can even do some polishing with the *back side* of the pad.
Sometimes you just have to do some spots by hand, but generally if you can get a portion of the PC's pad to touch it somehow, you can get decent results.
The PC is *so* mild that using the edge and other

techniques really aren't all that

But as I said, use common sense and remember that the paint on raised edges and corners is thinner than normal.
Oh, and when working stuff like the bottom lips of spoilers, try to have the PC's rotation working *for* you (running "off the edge") rather than against you ("running *into* the edge"). I do all kinds of lower areas by machine. I lie on a creeper and just push myself along, letting the PC do all the awkward work.