I have an easy way to remove wallpaper paste prior to repainting that uses a wet/dry shop vac and the floor squeegee attachment.   After removing the  paper, wet the wall that has the remaining glue, using a garden sprayer.  rewet it a few times until the paste is soft and soupy on the wall.  Take a scrub brush to hit any hard spots.  Then using hte wet /dry vac with squeegee attachment, suck all the wet paste off the wall.  The result is a nearly glue free wall that is almost dry.   I have a youtube video that shows the details