Hi Julia,
If the switchplate is sticky (like tape) and not gooey, I would recoat with another layer of resin. Otherwise, there is not a good way of getting the artwork back out without cutting up the plate.
The way I like to clean brushes is immediately after I’m done with them. I will use commercial (hardware store) acetone, then wash with a good detergent like Dawn dish soap or Tide laundry detergent. Some people have also shared on the forum they have had good luck with denatured alcohol.
Let me know what works for you!