Reddit mentions of Rust-Oleum 2422 DIF Wallpaper Stripper Concentrate, 22-Ounce

Here is the quick and dirty: Clear the room out as good as you can. Lay down painters plastic. Pick up a product called Dif and a tool called a paper tiger, available at hardware stores near the paint, or at regular old paint stores. Follow the instructions to apply. I use a pump sprayer to apply the dif mix. Use this style scraper but make sure you dull the blade's edge beforehand, or you will nick the crap out of your wall. I like to put a horizontal slice across the wall about chest high, then start pulling from that slice. Try to take the biggest piece off the wall that you can. Make sure you get both the wallpaper and the glue layer. The glue layer looks beige and fuzzy when dry but turns paper-bag brown when wet. When all the paper is off, go over the walls with a damp rag to remove any remaining bits of glue. If you have any questions let me know.

Source: painter

edit: You will need to reapply the dif fairly regularly, so I suggest wetting one wall/area at a time. Also added some info above.

I would personally strip it. Try a 50/50 mix of white vinegar and warm water in a spray bottle. Douse it down, let it sit for a few minutes and it might just wipe right off the walls with a scraper/trowel. You might try gently scoring the paper with a box cutter or an exacto knife before you douse it, that seems to let the vinegar soak in.

If that doesn't work, DIF should take it off.

I say this because if it's textured slightly I don't see how you're going to get a smooth finish if you paint over it.