Thanks for the feedback. Typically, I'm doing a long hauls between Hatteras and eastern Virginia - approx 250 miles each way. Then boat sits for a day or two, and then launch at a local ramp that is less than 1/2 mile away, so dumping hot axles into cold water is not an issue. I monitor the bearings closely since I'm carrying 6,000 lbs on a tandem axle trailer - check for heat build up while traveling, check for bearing noise after launch, and pump additional grease into bearing buddies to get out any water. The problem appeared to be just a bunch of crude built up in the bearing buddy springs that kept the piston from moving out when grease was pumped in.
After pulling the bearing buddies apart, it was apparent that the real problem was caused by corrosion inside the hub of the bearing buddies, thus the disassembly and cleaning. These were old BB's, that came with the trailer when I bought it used, so I'm guessing that there had been a major saltwater incursion in the past. Since I purchased the trailer all bearings, races, and seals, as well as brake shoes and backing plates have been replaced.
So, back to the issue - how to get the rubber seal back into the bearing buddy. I solved the problem for three out of four of the units by boiling the rubber seals in hot water. That shrank them enough to get them to go back in. One of them refuses to shrink enough, so I am on the hunt for a replacement. In the mean time, I cut a length out of it, to make it work on a temporary basis. The ultimate solution all around is to find a source for the replacement rubber rings. The ones I re-installed seem a bit stiff and not as pliable as they should be.
Here is another lesson learned - the groove for the rubber seal needs to be very clean to get them back in and working properly. The solution that worked for me was to brush the grooves with alcohol, then use a Dremel tool with a small flywheel-type brush to get them really cleaned out.