When I change a layer to 'lighten' then I create a white layer mask on it and paint with black to conceal parts of that layer I do not want, the brush works for most of the area I want to conceal, but then some still shows! I can not get rid of it. I do not have anything selected as it worked for most of the part I want to conceal, there's just like 10% of it still showing through. If I create a black layer mask it conceals it all no problem.
Please let me know what's going on!
Show some screen captures that show your issue. Make sure the important Palettes are visible and show your document layers structure. Uploading the layered document to a file sharing site and posting a link would even be better.