I'd did short Half hour to hour spurts Due to the physical part and having a family. I'd say in the 20 hour range also WEAR gloves. The black paint turns to liquid and stains everything.
I would have guessed 2x than. I removed paint off a crystal castles like 20 years ago and I learned never to try that again! Came out pretty good, but took days to do it.
I would think williams games are easier to do than atari. sprayed on should give your more room for error than exposing sticker art. Plus the hardest part is cleaning up the white areas.
I never thought of bubbles being that rare back when I got mine, but they do not show up that often. Considering I have 2 maybe 3 bubbles rom boards, most were probably gutted.