I have a 3/4 inch bow in some of my ceiling drywall. I can barely reach the rafter with drywall nails and I didn't use screws because the wood is so hard. I was wondering if I could jack up the ceiling with a deadman and then nail it, plaster it and let it dry before moving on to another section. Just nailing it doesn't work. The nail head pops through. It's not really noticeable from the floor looking up but I was concerned as to just how long the ceiling would stay up if I didn't at least try to secure it better.

You definitely need a deadman or a helper. The drywall is hanging down from the rafter, that is why your nail barely reaches the rafter. Therre is an extra 3/4 " of space between the drywall and the rafter. Good drywall screws should work fine, even in a hard wood. Nailing drywall on a ceiling is not fun and it can pop lose as you have found.

I have a 3/4 inch bow in some of my ceiling drywall. I can barely reach the rafter with drywall nails and I didn't use screws because the wood is so hard. I was wondering if I could jack up the ceiling with a deadman and then nail it, plaster it and let it dry before moving on to another section. Just nailing it doesn't work. The nail head pops through. It's not really noticeable from the floor looking up but I was concerned as to just how long the ceiling would stay up if I didn't at least try to secure it better.
Never use nails to install drywall.

Sounds Like It Got Wet. If It Did You Should Cut It Out , If Not A Dead Man Will Work Id Probably Use Some 2" Screws Instead Of 1 1/4, Nichols Trim

Chances are its going to crack when you secure it properly so your best shot is to remove it and do it over, screw from one side to the other. Don't screw one side then the other and the middle last because it will bow again and crack. Work your way from one end to the other screwing every 12 inches along the joist. Dry wall screws come in coarse and fine threads for every application and ceilings do require a helper

Do you have nail strips across rafters?