I had an issue with a vertex in the foot having a spurious positive weight in some unknown group that it had no business being in, and while I need to eventually learn how to debug this kind of thing, I decided to for now just restart my weight-painting from scratch because realistically, there weren't any great results in there that would have needed preserving.

So this time around, I started with the hip, which is always challenging. There's a big range of motion to consider and the question of how the crotch and underbelly should deform with the thigh movements. The easy way out would be to just have it stay put and ignore the thighs completely, but then if the figure goes in a crouch or squat, it's going to stick out like a sore ... umm ... thing that sticks out when it's sore. If, on the other hand, I let the thighs influence the crotch and underbelly, I have to mix the weights for both thighs very carefully so that the labia and other parts don't explode on me. So, that's where I'm at right now, and I haven't even mentioned potential complications with the butt and hip bone.

Here's a quick render of what things look like at the moment. Incidentally, I reduced the SSS scale from Blender's default value of 5 cm (2 inches) down to 1 cm, so I think her skin looks more skin-like and less waxy now.

-- I'm not mad at you, just Westphalian.