gummed tape (as opposed to masking tape) is not meant to be removed from the edges of your painting. It is used to stretch the paper to the board. When you come to remove the paper you run a blade around the edge of the paper (mid-way along the tape). The tape stays on the edge of the paper forever, this does not matter because if you have the painting mounted or framed the mount will hide the tape from view. Trying to remove it may result in tearing, smudging and is unnecesary. As for the board, you can just let it build up on the edges of the board until it becomes too thick then strip some off by pulling. There is no need to get it all off the board, just put the next layer on top.
Michele SAA PA