Anyway my question is do Magma Armor and Flame Body still work for halving the steps to hatch eggs in black and white 2? I know in the GBA games it did but serebii doesn't really explain if it still works or not.
Yes, it still works but it needs to be the lead in your party.
And remember the Day Care is only available in the post-game, so you can't breed until then. However, you can still use it to hatch traded eggs as well.