If there aren't any seals to damage by the pressure of the grease you can do it that way,in fact when I lubricate the U-joints on our machinery I look for fairly fresh grease to come out at all the bearings, but if there's a rubber boot or a sheilded bearing I'm more cautious as you could blow out the seal or push the sheild into the cage on the bearing, or push the seals off giving water and dirt a place to enter.