Darren,
You may want to check out the UNI-T 275 used for earth ground testing. It's not too pricey and may pay for itself and more depending upon what an electrician charges. Even if you use it once, it still has resell value. Keep in mind, now is a good time to break up multiple heads on one station if the wiring was run all the way to the satellite or valve box. It does change the programming needs and the As-built but worth it for control purposes. I posted an article on our website recently that details all the steps to satellite installation. It may be of use for you and or your irrigator.
Good luck and feel free to call me if you have any questions once you jump into it. We have installed well over 300 satellites.
Craig Zellers
(415) 342-1030
www.golfirrigationconsultants.com