Essentially it’s the same thing with new drywall and paint soaking in. Primer fills in the porous gaps better and it’s cheaper than paint. Otherwise you waste time and money having to paint upwards of 3 coats of paint and then it still be rough. A primer coat and a sand prevents that issue most of the time

BIN shellac is alcohol based, requiring you to clean up with either denatured alcohol or 1:1 ratio of ammonia and water. It’s also rough to breathe without a charcoal grade filter mask. I would advise against that option if you’re concerned about smell and dry time of the alkyd top coat. Some alkyd hybrids perform great! The above commenter is offering a solid option just has some disclaimers with it.

10 year painter and 7 year paint store manager here, it really depends on a lot of factors but for a reliable straight forward system I would say depending on how rough the wood is you may want to use a high build primer like XIM UMA (black and yellow label) because it’s also great for hard to stick surfaces if that ends up being an issue for any number of reasons. But a simple option could be to just use Zinsser’s 123 or your local paint store equivalent. Sand after primer maybe 180 or 220 grit. Nothing crazy, then 2 coats of paint. Beyond that the professional outcome relies first heavily on good prep work followed by good technique in the finish coat application. Hope this info helps