I am swearing off the transfer paper for good! I botched my 2nd carve last night because of difficulties/errors in transferring. Maybe I'm just not detail oriented enough. I'm sticking to sticker paper....pun intended!
Have you tried the Elmer's Washable School Glue Stick "Disappearing Purple"? That's what I normally use on the foamies that I carve. Cut out the pattern, rub the back of it with glue stick, place the pattern on the pumpkin and make any adjustments to the pattern (like little folds) while the glue is still fresh, then smooth out the pattern down and let it dry.
I usually give it about 10 to 15 minutes before I start carving. Once done carving rinse warm water over the carved area, the left over paper peels off easily and the left over glue turns back to purple and wipes off with a wet paper towel.
I like sticker paper too but I find it's not as easy to manipulate while sticking to the pumpkin....getting it into the curves and indentations of the pumpkin.