When I did mine (with ABS glue), I put a folded towel down on the floor, then the fender/extenda joint upside down on the towel, and set the front tire on top of it, letting the weight of the bike clamp the joint until it was cured. I was at the station anyway so it sat overnight.
If you pull it through the front of the forks, squeeze the metal gromets together (fender ones) to keep from marring the finish of the forks. Mine comes off even with the brace installed, too.
Don't foreget, with that fender and wheel off, nows a good time for some scrubbing bubbles!