Per the directions on the DIF container, mix some boiling hot water with the DIF. (Oh, first, buy yourself one of those HUGH car washing sponges from K-mart or Pep Boys or ADAP or any store that sells 'stuff' to wash your car with.) Put on some gloves and start washing the walls. Buy some Painter's Baseboard Plastic that's pre-taped and run it along the baseboard to 'catch' the loose water and glue residue. Have a 'clean' bucket of water to 'rinse' the walls. WHen you think you're finished, let the wall dry COMPLETELY. Then, with a hand-held light (of any sort), hold it very close to the wall to see if you can SEE any more residue. If you can, wash that part again.
Other than that, you can try scraping a little (but be careful. If you ding the wallboard, you'll have to spackle!) Sand paper will get gummed up so the more glue you can WASH off, the better. Sanding is the last resort but for small amounts of glue.