Once you've done a few they get super easy.
What tends to happen is the bolt is slightly bent at the split. So just removing the nut and trying to hammer it out is effective trying to drive a bent bolt through a straight hole. Easiest method is to use a hacksaw and cut the bolt through at the split. Then thread the nut on and as you tighten it , it will pull the now cut threaded piece through. You will have to put washers or a spacer under the nut once you get to the shank of the bolt but it only takes a few tries. Once this is out, you now have a clear shot at punching out the remaining part of the bolt. As the bolt is no longer bent/pinched it will punch out easy, even if it's corroded. Your welcome.