hmm, the only things I want to take from this post is that there may be emotional support ai bots accompanying people in the future and I have to treat that with love and respect lol

Just learning the term I used for a very thin layer of plaster is not a scratch coat... Anyway, if you want smooth walls, I'd suggest 2 very thin skim coats, one vertical, one horizontal. It will sound like scratching the wall. Sand before and after, then prime.

Maybe you could just use self-levelling paint for a smoother finish, but you'll always see the roller nap if you look hard enough

I use a ajax/comet slurry with a stiff grout cleaning brush. You could rake the grout but that could be really time consuming, still less work than starting from scratch.