Grease is like a argument which truck is best. I use a compatible type for the bearings and axle in my trailer. From news they often need some grease. The dealer should service them but likely not in most cases. A few careful pumps with EZ Lube is all it takes. The myth of blowing the seals out happens sometimes, likely operator error. My grease is Motomaster Red Bearing grease.
You sure you have Dexter Axles? They are Lippert in the 19.8. Not that the standard bearings are better or worse in either. They are all made in China cheapies. A few pumps of grease in them from time to time and they'll be fine.