Since you're having some troubles, you didn't mention that you're using a Paper Tiger. The Paper Tiger is used to perforate (not 'gouge') the wallpaper first, then allow the DIF to penetrate through and behind the wallpaper to get at the glue. If you're just 'wiping' the DIF on the surface of the wallpaper, you won't have much success in the DIF getting at the glue.
Check out a Follow-up I did a while back (among others) that will refer you to more 'tips' on how to do this job. It's a popular question on the Forum. Wallpaper Removal Links is a start. I'm not much for 'home made solutions' because I've have excellent success with the DIF. As long as you can get the DIF 'behind' the wallpaper (by perforating it with the Tiger), it shouldn't matter what type of wall you have. The Tiger is only a few $$$ at any Home Center or Wallpaper Retailer.