Please help! Eeek

[kalicokat.livejournal.com]

After reading so much about people using Mod Podge to decoupage with, I went out and bought some. I had this awesome idea, and I took a pair of black ugly looking heels, and magazine clippings and completely redid them. Yay!
But theres a problem. While the clippings are all staying glued together pretty well, in certain parts, they're starting to lift up off of the material on the shoes. I've put a few coats over them and have tried to stick it all back down as well as I can, but it just wont stay!
Is there anything I can use on top of it at all to fix the problem? I'd love to actually wear these (I live in texas so the water factor isn't really a problem). Im thinking maybe I should have sanded the shoes or something before hand, but I don't want to have to peel everything all the way off and redo them after all my hard work. I spent like 5-6 hours all together cutting things out of magazines and glueing them on.
So what can I do to make it all stay put?!