I don’t know if this is the right location to post a question or not so if it isn’t can a moderator please move it. 
Question 1: I am trying to paint a figure but I only want the paint to apply to the geometry that is sticking out and not in, or in other words the areas relatively equal height to where I start painting. So for example I don’t want to paint inside the cracks of a model. Now I tried doing a cavity mask then painting but it doesn’t get the exact desired results for two reasons. One I can’t compare the color contrast without deselecting the mask because the mask darkens my geometry, and two it doesn’t mask everything the way I would anticipate it should.
The closest solution I have found so far is selecting a standard noise brush and using it to paint color, but this also doesn’t give the exact desired results.
Think of the brush behaving like painting a plastic miniature. If I did a base dark color and wanted to paint on highlights I could easily dab my brush on the model adding paint only to the most exposed areas and not the creases and cracks, thus making a sense of depth with my paint.
Question 2: I need to make a mask with a lot of sharp corners that is in the middle of my model. Using the lasso doesn’t work because I can’t get straight edges, and the curve mask doesn’t work because I can’t select a closed geometric shape, only one side of the curve or the other. Is there a way to get a selection of a closed shape that has straight edges, like a complex letter Z for example?