Ed, it varies depending on wood, temps and sunlight. Some woods it "cures" enough fairly quick - a few days. Some it takes a lot longer. I've found poplar and willow seem to take forever to really cure. By cure I mean no oily sheen on your fingers when you handle it and to be sure you can place it on a piece of computer printer paper overnight. If there's an oil ring then maybe let it cure more. Warmth and sunlight help a lot in the curing process so this time of year I give it 3-4 days in my shop. When no oil sheen on my fingers I move on to finishing with shellac. All that said, I don't think shellac is finicky at all about what it goes on. I usually put shellac on the next day when all I've used is Yorkshire grit paste.
When rubbing shellac on I put a few drops of mineral oil on my application pad then put shellac on and rub it on the piece. The mineral oil doesn't impact the shellac and it helps the pad glide on the surface to give a much nicer shine. Counterintuitive to put oil on the pad and then shellac and rub on but, it's what I picked up from watching the furniture guys online.
Also, most store bought shellac has wax in it. You can buy or mix your own dewaxed shellac which is what I do. I use it for my go to finish where I want a glossy finish.