My boyfriend helped me change my first flat at home over the weekend and I rode the same trail again tonight and got a thorn in the tire again. (Front tire, luckily) Managed to ride it back to the car and brought it home to change and patch. All went pretty well until trying to get the last 8 inches of the tire back on the rim (knobby mtb tire). I just can't seem to be able to push the @#^$ thing in! Any tricks? I have a little arthritis in my thumbs and not a lot of hand strength. Help!!