My technique is to wet sand between coats and do a wipe down with denatured alcohol (both the epoxy fill coats and the varnish coats). The alcohol does a great job of removing dust and other contaminants, isn't too hard on the skin and doesn't leave any residue. I clean drips that may have formed in the epoxy with a card scraper. Timeline is not super critical with MAS Epoxy, I'm not sure about the epoxy you are using. Just be aware that area temps can impact your dry time. Regardless, I'm sure not getting up at 4 to do finishing work.

If I can get to it the next day, I do. If not, it will keep just fine. You just need to make sure that the epoxy is solid. If it starts filling the sandpaper, it is too early.

Eric M.