Hello World! My first guitar project

[McCreed]

Your logo may not be perfect now, but I reckon you'll get it near there if you keep going the way you're going! Good work!

I think that will be the end of it, then I'll leave it hanging somewhere safe for 3-4 weeks before wet sanding. I'll probably start at 800 grit and see how that works. There's some trouble spots but thankfully mostly under the pickguard. I'm apprehensive about the edges and corners, but I'll go slow and see how it goes.

14-21 days is generally long enough with polyurethane, but there are always variables like coat thickness and environmental conditions to consider. The "sniff test" is a good standard.

IME, with hand-applied poly, you might be able to start with 1000 or 1200. You don't get orange peel like you can with spraying so it may not require much levelling to get a nice gloss.

As for the corners and edges, I recommend either just lightly touching them or not touching them at all (unless there is a significant defect that needs addressing).
It's the larger flat areas that reflect the the most light (ie: gloss) and when you do the final polishing and buffing, it should be enough to shine up the small radiused areas.
Those same areas always seem to have the thinnest layer of finish on them and are notorious for sand-through. When I spray my finishes, I always make passes with a focus on my edges and they can still be problematic.

If you are going to foil screen the cavities, there's not a lot of point painting them.

Good point from Simon there, and one I was also going to comment on. I would add that regardless of the shielding method, it wouldn't hurt to seal the cavities with a few coats of shellac or poly before wet sanding. It just prevents any absorption of water and potential swelling of the wood. There shouldn't copious amounts of water getting in the cavities, but better safe than sorry IMO.