No, but it has to be in a 2:1 ratio between height and width. Then you can just follow the directions and you'll have an infinity cube that works perfectly.
You can use rags instead. However, paper towels are not going to leave fibers behind that could later block your gun when it is in use, causing you to strip...
Yes, you can use any paper that is easy to handle (printer paper, construction paper, etc.). But make sure that the paper is a square and has equal sides (unless...