When I made mine, I just layed them on some fine sandpaper, and it made the writing pretty easy. It keeps them from shifting around.
From the siggy swap, the other thing I learned was that I had to move my needle over about 2 "hairs" from the pencil mark on my squares, and then when I pressed them back, they came out pretty good. Still had to square them up a little, but they were big enough that way.