+1 to the mirror suggestion.
Masking is always useful for the plumping step, allowing you to isolate the top from the bottom. You should add some more volume to the area above the top lip as well so that it doesn't sink in so much.
with the dam standard brush do you use it with an alpha? when i first downloaded it and everything it has like a soft dot alpha but i noticed it doesn't seem that good for really cutting into the mesh
You shouldn't need to download it anymore, it's just sitting in Lightbox. I just used it's default settings (where the alpha seems to give it a sharp falloff).