you can not ready use it for large areas, nor does it work so well for dark areas, but lets say you where doing a portrait and maybe you where a couple of layers in, so your darkest areas where maybe a mid grey colour, lets say you painted an eyelash in completely the wrong direction, you could empty your paint cup, clean your brush, then put some cleaner in your brush, set your psi to about 2 or 3 get real real close and just gently (task gently) spray so little cleaner on the line, it will knock it back a shade or 2....obviously cleaner iss more eatery than paint, do you have to be careful not to apply so much that you may get a drip form.....you don't want it running down your canvas......imagine you where using it like a little sandblaster or glass etcher