Hello - long time lurker here.

I removed my baseboards before refinishing my floors from bare wood with Bona Traffic Naturale. It’s only 24 hours into curing, but that’s besides the point.

I’m going to get to a point of installing new baseboards & spraying them along with all the other trim, and I hear masking tape is a no-no, and I imagine even more that soon after curing.

So what is everybody doing for clean lines? I’m
Going to have to scribe the baseboards in some areas to deal with irregularities (no shoe) & may not be able to slide paper under there.

Some people coat the base boards while they are off. I like to provide the base boards, 16 foot primed pieces, ahead of time so the owner can apply a coat of paint before they are installed. I recommend sanding lightly with 150 grit no
fil paper to get them really smooth. Use a roller to apply the paint, then lay-off with a soft bristle brush so the finish is not stippled. After installation, which sometimes requires a block plane to fit to the floor, or even an electric planer, the nail holes can be filled with Crawfords Putty and the top edge caulked. Then small touch-up with a little brush while the paint is still fresh..
If you want to paint the flat area next to the floor, leaving the top detail nail free, you can use a paint pad that has little rollers at the edge which keep the paint off of the floor.