I found in a video for watercolour that when you put wax to create highlights that it can be removed using a hot iron by putting a paper over the painting and a piece of material on the back side of the painting and iron it on the back side. I tried it and it removed some of the wax. I painted over the highlight and the colour showed. Try it on a scrap of wc paper before doing on your artwork. Video called "Wax Resit Removal"