Title should say "done" not "some" 

First, if it's truly rubbery, you shouldn't be sanding yet. You need to wait until it's too hard to dent with your thumbnail, then test sand a small part. Sanding should produce a dry dust. If you're getting a gummy mess that clogs your paper instead, you need to wait a bit longer and test again. Depending on the temperature and such, it could take anywhere from a day or two, to a couple of weeks to cure enough for sanding.

Next, when you say "the bumps the fiberglass adds to the epoxy", do you mean the weave pattern? If so, here's an excellent article about filling the weave.

You can tell when you're finished because the entire boat will be dull and it will be smooth. If it's not smooth, after sanding the dull areas are the high spots and the shiny ones are the low. You need to sand the highs until you're almost going to cut into the glass with the paper, stop, add a thin layer of epoxy, wait for it to cure and do it again until the whole boat is dull and smooth. If you have a really smooth area and another one with lots of shiny pits, don't put any new epoxy on the smooth part. Fill in the pits, instead, and work on smoothing that spot.

Judging by the shine and orange peel texture in your photo, you've got a bunch of sanding left to do. Here's another article about sanding, and yet another about sanding and finishing. All these articles are in the CLC Shop Tips but there's so much good stuff there that sometimes it's hard to find the right one.

Good luck,

Laszlo

   Orange peel is a helpful term, now I know where I'm at. I've read all the articles three times over but didn't click where I'm at in the process. Heck the instructions just say until smooth.

Thanks!

   Update to anyone who might search this, I learned my thumb was moving my dewalt sander speed dial.  After upping the speed things felt much better.  I still spent about four more hours sanding before putting on my last layer of epoxy but I felt I was making progress so it went by much faster than the first 4 hours.  Don't forget to "tip out" it makes a work of difference and is super easy.  The boat looks pretty glassy now,  not perfect but much better than the "orange peel" in the photo.