You should be using a Paper Tiger, and only pressing hard enough to perforate the paper. DON'T press too hard or you'll be asking 'us' how to 'fix' those 'depressions' you made w/the Tiger.
If you read the DIF container, you'll see that you need to do 2 coatings AND you should be using HOT water. BOILING hot water. Use rubber gloves so you don't burn yourself. I use one of those HUGE sponges you wash your car with. And I lay out some plastic along the baseboard to 'catch' whatever drips. I only do a wall at a time. And if I need to do a 3rd coat (because the 2nd one dried up before I could get to it), I do it. The DIF is cheap. Be sure you are refreshing it regularly. It's worth it AND it makes the job that much easier. After a few walls, the solution gets cold and 'contaminated' from the sponge being dipped into it a lot. (Who knows what's on the walls ...)
And lastly, once you're completely finished the room, get yourself a CLEAN solution of DIF and wash the walls. Again, be sure it's refreshed when it starts looking like it's not doing the job.
Take all these 'tips' and you should do fine. My best to ya and hope this helps.