I have tried all the methods you mention but keep coming back to paper. I don't have any old phone books but have used some stock booklet that my son gets every year. Its pages are similarly thin. I bought a pack of Carol Doak's foundation papers and usually cut them down to 8.5". I find this easier than cutting muslin squares which also end up making the quilt too heavy. I also find dryer sheets too flimsy. The none-of-the-above method always ends up with too much distortion for me.