If your hub has a rubber plug, pop it off and you will likely have a grease zert staring at your face if you have Dexter Torflex axles. If you have the grease zert style, you can simply slowly pump grease into it and you will displace all of the old grease out around the nut... stop once you see new fresh grease coming out.
Anyhow, here is a link to the service manual for Dexter electric brakes..... Most of them are equipped with self adjusters, but if not, they list the procedure to adjust them. (remove rubber cover on brake backing plate, tighten star wheel with screwdriver working through slot, then back off star wheel until brakes just release providing a barely perceptible drag).
http://dexteraxle.com/i/u/6149609/f/6-8K_Service_Manual_6-11/Electric_Brakes_6-11.pdf
Here is a link to the hub manual.
http://dexteraxle.com/i/u/6149609/f/6-8K_Service_Manual_6-11/Hubs_Drums_and_Bearings_6-11.pdf