I recently removed wallpaper from our dining room. All of the walls have a molted appearance due to a blue residue (the darker streaks in the attached file) remaining on areas of the walls. I've removed plenty of wallpaper before and this doesn't look or feel like glue. It comes off after a significant amount of rubbing with a rag and Goo Gone or Goof-Off, but that amount of work isn't feasible for a room this big. I've also tried wallpaper paste remover and a vinegar/baking soda combination, but nothing seems to work even after upwards of 45 minutes of waiting. What is this, does it need to be removed, or can I prime over it before painting? Alternatly, could I seal it first with a product like Zinsser Gardz?