I candle only at night, and I put an ! with a marker if I think it is viable, and ? in marker if I am not sure. I do this every week, so when they are ready to hatch those that go into lockdown, should have 3-4 ! mark on them. I use the X and O for turning them. Just what works for me, and keeps the guess work down for me.
eta. I stand right next to the bator and candle one at a time closing the lid while I candle. Everyone will do it different, you will find what works for you.......
Thank you! Luckily the bator has an auto turner, phew! I couldn't imagine turning 42 eggs several times a day, by hand! Are you worried at all about the marker on the eggshell? I ask because I have read to use pencil or a grease pencil as the shells are porous. I know everyone does it differently and hearing from others who have done this just helps me formulate a better game plan.