I've found the I can lay on my back, feel for the plug through the window with my left hand while wrenching the engine over with my right.
This is the way I do it too.
I will caution - be particular when you are "feeling" for the drain plug as you rotate the engine. You do not want to be pressing too hard on the torque converter. The drain plug can get the end of your finger and catch it between the side of the housing (pinch point). Learned this the hard way
Eric - if this is your first time you fill as follows.
After fastening everything back together (don't forget to use new crush rings) you will want to pour 4 qts in the tranny, start up the car and add another quart. I always go slow adding it after I have about 5.5 qts in them to keep from overfillling. Anyway after 5 qts or thereabouts you will want to drive it some and get it up to temp. Then check/add as necessary.