Help! I've stripped the vinyl wallpaper from my dining room walls and removed the 2nd layer (backing)of paper beneath that. Under that yet, there is a thin residue of rubbery blue gunk (sizing?) that comes off haphazardly and in little, rolled up balls--kinda' like the old school glue--but not completely. We've tried the vinegar & water mix without success. How do I get this gunk off the walls so I have a nice, SMOOTH surface for paint? I detest "lumpy" walls! Thanks.