Just pump the cavity full of grease slowly and it will fill the cavity, bypass the seal, and fresh lube is in. 1 or 2 pumps regularly and you wont change another hub.
From my experience in industrial I will not force it in. That can cause more issues, probably not so much on a deck but in my line of work. I pull the spindle and pop the seal, on the grease side and leave the one on the blade side.
