I'll add this too - and again -
It is extremely important to roll the wheel as you pump the grease in!!
Also, continue to roll the wheel after you are done pumping in the grease. It relieves any pressure from the seal and the grease will get pushed out the front. Wipe all excess from the outer bearing.
I cut a small - 1/4" - slit in the rubber cap to allow for air expansion.
I've not had any seal problems with my method.
FOR SALE 2014 BOSS 6.2L F350
2012 Surveyor SV264