I always cover my eggs. Tupperware containers are cheap and work great for incubating. Its a lot easier to maintain humidity that way, at least for me. I'd suggest covering them with a damp paper towel and bump your humidity up quick!
If you decide to cut the eggs, a razor blade or scissors will both work great, just be careful. I have used both. Just make sure they are clean and keep a bottle of sterile saline on hand in case you have to replenish the fluids in your eggs. If you use a razor blade I would tape all of the blade but the tiniest little corner. Just enough to cut through the shell of the egg.