I didn’t use to stretch my paper but since I tried it once, I’ve been doing it with every painting. I wet the back of my paper, then front and depending on the size of my painting I use staples around the edges or a brown gummed craft paper tape. If I work on a half imperial sheet I choose staples, because I don’t have space for masking tape (my gatorboard is almost the same size). I use a gatorboard to stretch my paper.