The file-down step is where most people mess up.
Grab a coarse file and remove the shiny top layer along with most of the bulk. Soak in acetone for 15 to 20 minutes, and then push the softened gel off with a wooden stick. Some brands are hard gel and won’t dissolve at all, so if it hasn’t budged after 20 minutes you’ll probably need to file it all the way off. Get it thin and dull. Then it flakes off instead of forcing you to scrape forever. Put on some cuticle oil for a few days after.