I am using Pellon 906F, it is for lightweight to medium weight fabric. I have tried many kinds and this is the best. Follow the instructions carefully, the time to press in one place is 10 sec. which is very true. I use a steam iron on cotton setting. I place the tee face down on top of a teflon pressing sheet [www.softexpressions.com/software/notions/jtTeflon.php], then the pellon and then a regular pressing cloth.
They are easy to make.