After getting all of that off, GARDZ would be fine. Personally, I’d opt to using DRAW-TITE 325-W, ordering it on Amazon, just so that it covers everything. Both GARDZ and PRO-999 are clear. If you have a local hardware store like Ace, give them a call and see if they have GARDZ. I’m not a big fan of Roman’s PRO-999. Sherwin Williams has “drywall conditioner” that’s another similar product (again, not a big fan). In my opinion, I’d rank the products as follows: Scotch Paint’s DRAW-TITE 325 > Zinsser GARDZ > Roman’s PRO-999 > Sherwin Williams Drywall Conditioner. DRAW-TITE’s white tinted version is what I’d go with if I’m painting over it https://a.co/d/0410WQoY
