First off let me state that I'm using CS3 so I don't necessarily have all those new fangled, highfallutin, tools you youngsters have.
OK. For the double chin I used the poly lasso tool to make a selection of where I thought his jawline would be, starting just under the ears and going down to include the double chin. So I ended up with a half moon shape selection encompassing the double chin. I then using cntrl T scaled the selection up from the bottom, compressing the double chin.
That will leave you with a funky looking jaw line and a big hole in the neck. To fill in the hole I made a similiar shape selection on the neck just below the hole, copied and pasted it, then moved it up to kinda fill in the hole. To fill in the rest of the cracks, I used the clone tool and the healing brush. I guess my secret here(if it really is one) is to use a small hard square brush with the clone tool, zoomed in with small strokes. Your goal is try and blend with the surrounding pixels so sample a lot from surrounding areas. After an area is filled in I go back over it with the healing brush to finish blending it. It's time consuming, but the smaller brush you work with and the more time you take to make sure the pixels are blending right, the better it will look.
Now that the neck is filled in you still have that funky jaw line to deal with. No secret here. I just go in with a small, square, hard, low opacity brush and paint. I eye drop the naturally occurring shadow portions of the jaw and basically stipple in the jaw line where it need shadow and sample from the lighter portions to stipple in and blend where it needs to be lighter. There is no such thing as a solid line in a photograph and I think that's where people make mistakes. Your not really recreating the jaw line, your mixing and matching little square pixels of color to give the illusion of a jaw line. As soon as one realizes that there are VERY few quick fixes and just say's damn! this is going to take a while, but the results will be worth it. Their work will improve tenfold.
OK. Let me step down off my pulpit here and try not to fall on my butt...
Smoothing out the faces is a mix of healing brush to get rid of the obvious blemishes. A custom blending brush I made and a trick I picked up off of you tube.
Like I said, every photo is different you will have to adjust your process as needed, but that's the basics of it.
Hope it helps.
