I hope you used a radiused sanding block with all that sanding to keep the board true. I had to remove a botched coat once (although it was dry). As long as you use coarse grain sandpaper and switch out the sheets every time it gums up, it really doesn't take that long.
I've done four epoxy jobs now. The secret IMHO is to do small coats each time. Thicker coats dry more unevenly and slowly. Mix thoroughly and gently to avoid bubbles. I've also begun mixing in a little denatured alcohol with the epoxy. I use two parts expoy, one part hardner, and one part denatured alcohol. The alcohol evaporates and doesn't seem to affect the epoxy setting up. It does seem to help with the bubbles issue. Any bubbles that form are easily "blown" out. I've stuck to using mirror coat. Never had any problems with getting the mixture of epoxy to hardner. Either I've been careful, lucky, or mirror coat is more forgiving.
I actually prefer the livelier response of epoxy to rosewood. If it is too clanky, I'll either roll of the tone knob or just let the strings get a little older and gunkier. Then again, that's with rounds. I dug the flats on bare wood sound for a while, but rapidly started missing the clarity and articulation of rounds. Back to rounds again. If you want to solely use flats, then epoxy isn't needed for protecting the board.