I have used the cheap plastic hand pump that you guys are talking about, the one that screws on to the top of the bottle. There is a better way, It's more expensive but I think it's worth it. Go to
http://www.stevensinstrument.com. they have a gear filler, basically it's a pressure pot. Put your gear lube in. Pump it up. It has a hose with quick disconnect fitting and a shut off valve right at the fitting. Screw in the right adapter into the lower filler hole on the drive. Connect the hose with the quick disconnect and then open the valve. When the gear lube starts to come out of the air vent, (the one under the plastic cover), shut the valve off. Install the air vent plug. pull the hose off at the quick disconnect. Then quickly remove the adapter and put in the lower plug. It's quick and easy and you don't get any air hung up in the drive where it shouldn't be. Plus the gear filler is made of steal. It will last a lifetime. I have also bought the vacume tester and the pressure tester. You can test the vacume and pressure to make sure there are no air leaks in any of the seals on the drive. Like I said. it's definitly more expensive but it will last a life time and will give you peace of mind to know you did the job right. Stevens instrument also has all the adapters for all the different drives.