I do have the EZlube spindles, and for now I have the bearings packed and the spindle loaded with grease, not sure that matters. I've packed them like this before, but after one or two trips I can't add more grease without filling up the hub if I leave the tire on. So I guess I answered my own question, knowing that it is impossible to keep all water out the hub will have to be full to push old grease out. I do like the idea of the pneumatic grease gun although not sure how it would work on road trips, wonder if there is a dewalt version.

There is a member on here RT930... he was the oil bath with air pressure, loves them and next to nothing maintenance from what I've heard.

I believe all the name brands have battery grease guns now.

I just pulled all my hubs and did the full maintenance on them. I made sure to polish the spindle where the seal rides so I wouldn't get any leaks. I cleaned the bearings in mineral spirits and blew them dry then I used a bearing packer that does a good job quickly. I only use Amsoil marine grease as it can handle up to 10% of water dilution. I have the EZLube spindles and with a pneumatic grease gun I filled the hubs. I'm in and out a lot and didn't want too much air in the hub to suck water in when I dunk the trailer in cold Lake Huron. Most of my trips are less than 50 miles round trip so I don't do them unless I notice a seal starting to leak or moisture in the grease. It's been almost 10 years since they were done last and they were still in good shape.

Best hub system. no fuss no mess. I trailer cross country with our 400SS...heavy. Never had a bearing failure or water in a hub. Pre launch just make sure the front boot is pooched out a bit.
https://www.airtighthubs.com/