If all else fails, then the work will have to be moved to the ground, (hard like concrete)
and a few choks of timber will have to raise the work.
I imagine things are bouncing off that work surface, leading to more unnecessary hammering, compared to only one or two solid dead blows.
A club hammer surely will be able to do this without taking much of a swing at all.
And as said above, a dip in something overnight would likely help matters a fair bit if it won't move, and less chance of damaging (mushrooming) the end of the shaft.
All the best