If you have bearing buddies you can't overfill with grease. There is a hole that excess grease will come out of if overfilled.

When I come back from the salt,I flush at the ramp if there's a feshwater hose,or I do it in the driveway at home. Just take the nozzle off the hose,and flush each side for a minute or two.

If it's a new trailer,check the warranty. My trailer warranty had a 5yr warranty on the hubs,as long as you never mess with the bearings,or remove the buddies. To service the bearings on my trailer,all you do is fill the hub with fresh grease from a zirc fitting on the buddie.

I also check the temp of the hub every time I stop for gas or food,it only takes a second to reach down and feel the hub.

I was leary of the maintanance with the bearing buddies,I was used to messing with the bearings every year,just to be safe. I have almost 40k miles on my trailer since 1997 and have had no problems yet......knock on wood.

You may want to look into servicing your trailer yourself,it's super easy to replace and repack bearings. My mom just had a bearing service done on her fifth wheel.....$200. I wish I woulda known,I'd have done it for free.