Probably kind of late for this time Tony, bu t maybe will help someone.
Ran electric to the family's barn last year, barn's been there 70+ years and only served by 200' of extension cords. Needed to drive an 8' ground rod for the new sub-panel, and was dreading it based on situations similar to yours. I accidentally came across a video similar to this one
and figured no damn way in our hard clay. I had all the various hammers ready, but actually only needed a quart bottle of water and about 5 minutes to get the 1st 6 feet of rod in the ground. Had to pound the last 2' with a sledge, but I'll be dipped, it actually worked.