I wouldn't use the Bearing Buddy. As the article jeffnick's post links to the grease is constantly under pressure and gets forced out the grease seal and onto the brake surfaces. Once that happens you will not have trailer brakes and the grease will be adsorbed into the brake shoe material. Once that happens you will need to replace the brake shoes as it's impossible to clean the grease out of the contaminated material.
As for keeping water out of sealed bearings, it there is enough water it will still get into the bearing. In the recycling industry we use water to keep the dust under control and help separate the trash from the metals. We would grease the bearings every 10 hours per manufacturers directions until fresh grease pushes past the seals. Every time we greased the bearings there will be some water inside. Happened everyday for 26+ yrs.
Richard & Jill
2014 Flagstaff 832IKBS Classic Super Lite
2018 Silverado 1500 Crew Cab Z71 4WD All Star Edition
Camping since 1989, seasonal since 2000
Car Shredder Op/Tech, Scrap Metal Recycling - retired
The Faster I Go, The Behinder I Get.