If you overpaint switch your color from black to white
If you want to be more precising in your painting:
Zoom in with Ctrl and +
Continue painting.
If you overpaint, switch your color from black to white. Then, as we begin painting in white, the black and white adjustment layer will be shown once again. Paint over the places you overpainted.
When you paint over a mask, we also recommend to change your hardness from 80% to 0%:
Go to Hardness at the top middle.
Select 80% with click and drag.
Type 0%
Press Enter.
If you are painting in 100% hardness then your brush will be very harsh. But, if your hardness is 0% hardness, then you can blend the areas of the picture they have the mask black or white.
By using 0% hardness and switching your color between black and white, you can paint precisely on a mask to apply a layer exactly where you want it. Just make sure you have the right layers selected before you begin painting.
For example, if we took our original photo and apply a mask to it, there will be a difference whether we have this mask selected or the black and white adjustment layer. If we have a Black and White adjustment layer selected and then we begin painting in black, we will hide the Black and White adjustment.