Ok, here's a slightly silly question. I used to coat with a sponge brush but wanted to try glass rod coating for its smoothness. I find, though, that the puddle keeps expanding along the length of the rod as I push, so that I don't get a rectangular coated area. My glass rod is quite long but I am wondering if it needs to be just the right size. That is, if you have an 8 inch rod for 8x10, can you also coat for 4x5 with it (if so, how do you do it?)? Or do you need a rod just 4 inches for that?