1) For painting directly onto a layer? Almost never. Painting is for masks.
2) Avoid doing so if possible, or if unavoidable, use multiple radial gradients.
Thanks.
I finally understand what you mean about the halo. Sorry about my denseness.
But it's no biggie. I just used a little bit of burning on a D&B layer.
Download PSD
I need to see the whole photo. Before and after your background fix.
And no, there's definitely no banding there. It must be your screen. What screen do you have?
You'll need to be a LOT more precise with your masking than that.
The only place, ironically, where you don't have to be very precise is on the hair. For everywhere else, you'll need to zoom way in, and use your Shift key.
How about a Levels layer, and on the Green channel move the white Input slider to 240, and on the Blue channel move the white Output slider to 180?
Fiddle with those numbers as you see fit, of course.