I want to put the final coat(s) of wipe on poly over a gloss poly next to last coat of material. I previously applied many coats of Gloss polyurethane, but now I need to finish this project today. Can I puddle some epoxy over a few little problem areas, so that I can sand and put on a final cost of wipe on satin poly?
Use a small quantity of yacht varnish. I will fill your irregularities and when it is thoroughly dry you can sand it flat and proceed as planned. Polyurethane will not fill holes in itself very well.
Since it's due in a day, and this is a year later, I suspect that I'm too late. That ship has sailed.
Epoxy I suspect is a lot harder than your other finish, and I think you will find that sanding it without totally destroying the finish around it will be difficult.
Since the problem is a 'hole' fill the hole with the same material you are using to finish it. Water based varnishes something like 30% solids, so you will need to fill it a bunch of times. E.g.: If your defect is 400 microns (.4 mm or about 1/64 of an inch) fill, let dry, it's now 280. Fill let dry its about 200. 140. 100 70 50 35 25 ...
You can get there a bit faster if the earlier coats have some form of bulk additive, such as fumed silica (used in fiberglass finish coats.) Ideally the mix will be close to the colour of your base material.
If you must turn in in a day, just finish your coats, and leave it. You can finish it later. The epoxy trick, may leave you with a destroyed finish that requires stripping and starting over.