I was really hoping someone had tried that rod driving accessory. For this job I had bought one -- and promptly lost it

No matter; both rods went into clay readily using an SDS-Max demo hammer.
Now: for the ground wire ("GEC", or Grounding Electrode Conductor). It has been my practice to run a #4 solid wire in EMT to the first ground rod. Since this particular location would have made the pipe a trip hazard and annoying to the gardener, I chose to use heavier pipe (RMC).
Starting at the panel, I used an intersystem grounding bonding device sold by Ideal. This device connected my pipe to the panel and completely protected the wire. The Phillips screw, when tightened, bonds the wire to the inside of the block. This is the only intersystem bonding device I've seen of which I approve. (first picture)
(I'll post additional pictures separately. I wish to encourage discussion on each detail of this job).