The old paint if its laytex paint if its laytex paint if its laytex paint if its laytex paint if its laytex paint if its laytex paint if its laytex paint.
wall paper glue and paint are a pain…..but a belt sander will cause you more of a pain.
well the glue should come off with warm water soaked on- try spraying it through a spray bottle, let sit, then take a scraper to it. you might try vinigar as some people say it helps with wallpaper glue removal (i never noticed a difference).
As for the paint- you are opening up a can of worms by sanding it with a belt sander. The small 1/4 sander works but will take forever to vibrate it off. this is a good idea to finish off with, you will have to do it by hand- the hardest way but will produce the best results!
If you have alot of raised areas where maybe paint is gooped up , paint drips, someone elses crappy patch job or where paint meets wallpaper- then your best off doing that by hand also- go buy a gooood razor blade scraper for about $10, that and a little elbow greese will do the trick. try using the scraper at different angles to smooth out the surface completely.
Dont try a regular metal scraper- its useless. (razors work best).
A belt sander will rip the paper off the drywall, or the upper layer off the paint , and will be harder to patch up neatly.
The age of your house you sick try priming the wall with one ps dont use block sander use block sander use an oil based primer then skim it wont kill you may make you may make you sick try priming the results are worth it may be sanding lead.