I only candle if someone wants a tutorial, or a photo. Personally, I don't see the point. If they hatch, they hatch. If they don't, they don't.
I seal the tubs when I put the eggs in, with press and stick. Then I open it to let a bit of air in around day 50. Once they start to pip, I replace the press and stick with the lid for the tub (with a couple holes predrilled).