I usually use whatever 8.5x11 sheet paper I have on hand. I've gotten rid of a lot of the packing lists and receipts that came in boxes from BMS, Uncle Mikes, etc that way, so it's not uncommon for an unpainted rocket to have a list of rocket-related part numbers and such printed on the fins... I typically use the fin pattern to cut the paper to size, then put a thin layer of Titebond on the wood and press the paper in place. I usually do this after I've sanded the fin edges round or airfoiled, and when the paper is glue saturated, it conforms quite readily. Layered between wax paper and pressed flat under weight to dry. I make a point of doing all fins in the same order (left side than right side or vice-versa) so that if they so have a slight warp due to the first side setting up before the other is finished, they will theoretically all be the same (thus give an "intentional" spin characteristic). So far, though, that really hasn't been an issue.