When working with acrylic paints the one product that will remove a layer from your painting or clothing is rubbing alcohol.
Recently I got gesso on my black jeans. I didn't notice this until it was dry - the next day I put them on the counter and puddled rubbing alcohol on top of that area and let it soak in. I used a small crochet hook and kept running that back and forth until all of the gesso was rubbed and scraped away. Success! After washing them I can hardly tell where the white gesso had been.
If I have applied a glaze to a painting and it has dried and I am sorry with the result I can remove most of that layer by spraying that area with rubbing alcohol and scrubbing it off with a paper towel. As well, a really neat burnishing look can come from this technique - while rubbing off an area - with valleys, grooves, textured areas... the colour is pushed into those crevices but taken off the higher points. This gives an aged look to the area and can be appealing. Sometimes this works great and other times areas can look muddied.
When I was working on "Field Notes to myself" and was almost finished I applied a glaze on a group of lighter areas in order to unify the painting Once that was dry I was disappointed with the result - it looked too dark and murky. I had run out of rubbing alcohol and it was late at night so I decided to try Windex, a 3M green scrubby and a Mr. Clean Magic Eraser. This worked great. I had used a lot of acrylic medium to adhere all of the collage elements so this gave all those areas flexibility and they could stand up to the scrubbing. I have continued to use Windex this way and it really works great.