Save your money on DIF and like products. Use a paper tiger and warm water.
Spray and let sit for about ten minutes. Spray and let sit again. The
trick is to let it sit until it gets the glue wet. Then scrape LIGHTLY or
peel. The best scraper I had was an old metal spatula that had just the
right spring to it and edge.

There is NO easy way to do this. Spraying and waiting is the best.

Go over it once you're finished to get all the snot blobs of glue and paper
so your paint job will look better.

I have done three houses. Don't ask me why. But, I have found what works
best. And that is hot water and waiting.

Steve