It takes a LOT of grease. Done right it basically purges all the old grease out of the hub thru the front of the hub. I use a red hi temp grease (one of the ones recommended by Dexter). When I see red grease coming out vs the old darker grey colored grease I know it is done.
Pump slowly with a hand pump. Don't pump too fast. Don't force it. All while continuously turning the wheel. And it will work well. Some have had a problem pushing grease thru the rear seal and ruining the brakes.