What's the best way to clean wallpaper paste off a plaster wall?

try soap and water or white vinegar and water

Try using equal amounts of very hot water & vinegar in a spray bottle. Spray small spots on the wall and use a plastic putty knife to scrape the loosened glue off the wall. It's time consuming but it works.

Scrub the wall with a scrubby and hot soapy water.

Try using diluted fabric softener,or a product called Krud kutter.

Try TSP cleaner - no rinsing and works on washing down greasy cupboards b/4 painting

Use ammonia mixed with Don dish detergent. Spray it on and use a scratchy type sponge. It's a tedious job. You have to go over and over and over it to get it all off

I used equal parts hot water and white vinegar in sections then meticulouslay scraped those sections with a thin metal scraper. Then wipe down the walls with clean water. Then use a good primer before you paint.

There are any number of videos on YouTube with step by step instructions as well as a number of solutions. https://www.youtube.com/results?search_query=remove+wallpaper+paste+from+plaster+walls

Using vinegar and water or soap and water works but after you clean the walls you will need to put on a primer sealer coat before you paint the walls with the final color. I didn't do that the first time and the paint eventually pealed off my walls. There are several brands that will work. Check your local paint store.

l use a product called Dif. You score the wall paper with a Paper Tiger, then follow the directions on the Diff bottle. EASY PEASY. It gets right into the glue backing and makes it come off the walls cleanly without having to use elbow grease. Then, prime and paint.

I used vinegar and water no a hell of a lot of elbow grease. I was not impressed w diff. In fact it made the process even more messy. It took me about 3 weeks of spraying with vinegar/water solution, waiting until it soften, scraping it off w a plastic scraper, allowing it to dry thoroughly and doing it again. The last phase was to use a hand block sander and scuff up the spots that remained. Then I did use a primer first. I was happy with the final paint job

Use dish soap and water.

Thanks for all your helpful ideas. I use your ideas when I did my kitchen wallpaper paste removal and found it was very time consuming. I just hoped there was an easier/quicker solution.

use household gloves

I would try a steamer and a putty knife.... I find that my little Shark handheld steamer is a lifesaver when dealing with anything sticky or adhered to any surface.

Try fabric softener with hot water