I've read all sorts of ways to do this. Special tools, by hand, duct tape, etc. etc.
However, I've never heard anybody mention this.
Use a grease needle.
Just slide the needle between rollers. Pump till clean grease comes out. Work your way around the bearing. Works awesome. You waste hardly any grease, the old grease gets pushed out by the new, and the bearing is usually packed so tight you can't turn it by hand. Heck, sometimes you can do it with the bearing still installed.
However, I've never heard anybody mention this.
Use a grease needle.
Just slide the needle between rollers. Pump till clean grease comes out. Work your way around the bearing. Works awesome. You waste hardly any grease, the old grease gets pushed out by the new, and the bearing is usually packed so tight you can't turn it by hand. Heck, sometimes you can do it with the bearing still installed.