There are numerous ways to check the ground rod resistance, this can be a fall of potential test which uses somewhat expensive testers, it can be a clamp type meter, you can actually apply voltage and use an amprobe. The truth is, the required 25 ohms at the ground rod doesn't mean much at our voltage levels, and unless you are shooting for some "performance" level of grounding, you are better off just driving two rods and then head to the house. [Linked Image]

Roger