Pain that it didn't quite go as planned...

I have no experience with pouring epoxy for rails, but from having done other things where bubbles can be a pain I definitely suggest thinking about putting the epoxy in a container you can seal and plug into a vac pump or even just shop vac for 30 mins to de-aerate... if you can vibrate it at the same time (I sometimes use an old orbital sander stuck onto the container) it speeds up the process.

Once poured, is vibrating the frame an option? Can help bring bubbles to the surface.

Better luck for round 2!