There have been reports of some axles coming dry from the factory, so for peace of mind, pull them all and repack them, even if there is EZ-lube. For grease I have been using Moly based bearing grease like this
which is for Fords. I have tried other brands, but this one seems to have the highest Molybdenum content of any of them. Moly is a great lube, better than any synthetics, but hard to contain, it falls out of solution, and this grease seems to hang onto it the best.
Note to take, if you DON'T do like Beck said when pumping grease in, it is possible to blow the rear seals. This is especially true if the trailer has not moved for a long time as grease tends to firm up and a blockage can occur in the bearings if they are not rotated to move the grease around. It doesn't go past the lip on the spindle, it can actually push the seal out of the bore. Seen it happen a few times, so always use caution with pressurized lubing systems.