I just redid mine yesterday. I have always used a pc of batting but noticed that the blocks recently stopped sticking so i turned it to the other side and it sticks alot more. I know it is better to use 100% cotton batting as the blocks sticks best (so i have been told), but i found out if using the 80/20 use the soft part of the batting as the sticky part (meaning the side with the scrim should be against the wall).
Hope this helps