All you need is one hole to pump the grease in. This always worked perfect for me. I never got dirt in with just the one small hole. Cert Zerk yeah same thing my grammar bad sorry. lol I heard it by so many names..over the years.
With the coaster brake hubs I think its prolly still advised just to take those apart and clean them out. I never liked that concept I never used them. That's just me . Some folks like those and report good on them. Free wheeling cranks spoiled me.
Then there is the internally geared hubs that were not meant to have axle grease.