I would use bleach while it's filling and switch to dichlor when it's full enough to start the pump. Wouldn't want undissolved / dissolving dichlor sitting on your fresh epoxy. Keep a close eye on pH while using the dichlor. It's probably a good idea to get pH, TA and CH tests of the fill water.

Are you filling from the hose? Did you check the water meter when you started filling - that would be a great way to know the pool's volume.