I am at the varnishing stage of my Petrel Play and I prefer brushing on the epoxy. I used a roller for a seal coat on my stained panels and it will produce a THIN coat, but it was also textured or "stippled" in appearance. You will likely sand most of it off.

If you only have a few minor dimples right now, a roller might be able to fill them, but the roller doesnt leave you much material to work with.

I prefer the brush because I can put on a good thick coat that will be easier to level in the end. Treat the epoxy like you would varnish, with consistent, methodical, cross pattern of horizontal & vertical brush strokes. If you dont put enough fill on now, you will just have to do it all again. I would rather put it on heavy and only sand it once.

Make a drip edge with masking tape at the shear line. Work from the keel to the shear, and any runs or sags will end up on the tape instead of the boat.

If you have sags on the boat, flatten them with a scraper before sanding. It goes quick and your boat will be smoother.

   A method for getting a more even surface, which I'll credit to Lazlo, has you lightly sanding after the second coat to bring down the high spots and to show the low areas (shiney). Next coat, rolled and tipped, should bring you to a near level surface, once sanded, with less chance of sanding through to the wood.