use a fence post driver.
Let its weight do the work for the firszt few strokes.
this is a long pipe witn one closed ehnd. it has handles on each side for 
grasping.

you place it over the rod, raise it up a foot or so and drop.
its weight will drive.
once you get it down into better reach, pick it up and really slam it down. 
drives very well. and no worries about missing with the hammer.