Here's a good way to do it that few folks know of.
It takes a little time to set up but you can save a lot of effort and can also fill the transaxle when it is stitting level instead of jacked up.
(please ignore the simplistic whay I wrote it, my feeble attempt at humor).
Get yourself about 4 to 6 feet of clear plastic tubing, 1/2" diameter.
Stick one end of it in the hole in the tranny. Safety wire or zip ties do a good job of making sure it doesn't accidentally fall out and dump your incredibly expensive stuff on the garage floor. Duct tape isn't anywhere near as good for this particular job.
Stick a funnel in the other end of the hose and fashion a hook for the funnel out of coat hanger or whatever you have handy.
Hang the funnel on something, like a door window, etc. doesn't matter as long as it's above the tranny.
If the tubing is too long, now would be a good time to trim it. You don't want a bunch of excess tubing laying on the ground, just enough to get from the funnel hanging place to the tranny.
Place a drip pan under the transaxle so that any fluid that drips out doesn't make a mess. This is also handy to catch any excess oil in the tubing after you are done.
Here's the tricky part: pour the slippery stuff in the funnel. Don't go too fast or it will make a mess. You don't want to spill the oil inside or on your car. I prefer to hang the funnel on something other than the car like a floor jack, your choice.
Stop when you get about 3/4 of a gallon poured in and check to see if the tranny is full.
Keep going until it is full.
Stop pouring the oil in the funnel when the oil stops going in the tranny and starts going in the drip pan.
Wait for a few minutes and pull the hose out of the tranny, put the plug in, wipe the side of the tranny off, slide the drip pan out without spilling it (easier said than done).
Remove the funnle and hose, making sure not to dribble it all over the garage.
go for a drive or have a beer.