Once you’ve skimmed everything down, carefully pull off your stencil. Make sure to do this while everything is still wet. You don’t want your stencil to dry into your plaster!
If you notice parts that are smudged or out of place, you can take a small tool, like a tiny flat head screw driver or a pointy knife and clean up a little bit. If there are really uneven parts or areas that are looking too high, wait until everything dries and sand down where needed. But remember, imperfections can add really nice character to your stenciled look. Plus you are painting over later, disguising smudges and such.