When you do the trans pan start by 1)removing all the bolts from one side. 2) Then remove the closest bolt from an adjacent side. 3) Next remove the closest bolt from the other side that is adjacent to the side with all the bolts removed. 4) Repeat 2 and 3 until all bolts are removed from these two sides (there should only be one side with bolts left), as you repeat 2&3 your trans fluid should start draining from the fist side, slowly at first and then more aggressively as you remove bolts. 5) once you've drained as much fluid as you can slowly remove the bolts from the last side one at a time time, more fluid should start draining especially once you start to remove the very last bolt.
This is the best way to drain the trans pan without making a huge mess 😉