About the best place to get out ALL the oil is tapping a 3/8 npt plug into the transmission cover
Due to the angle the motors are installed and lack of oil filter I found the sediment settled in this area over the years
Seems like a nifty solution.
Here is another. Indigo sells an oilfilter kit. It uses the existing oil change hole that was mentioned by someone else to circulate the filtered oil.
Incidentally, on my machine there was a manual pump in this hole which was a factory option on some machines. It worked well enough but was not fun to use. And I wanted the oil filter. The kit comes with everything you need, it is very well made, and it installs in a lazy afternoon.
Now here is the connection with this thread: The fitting for the oil filter has a connector for an oil change pump. I bought a 12V oil pump on ebay and installed it permanently with the oilfilter kit.
Now changing the oil involves putting the oil hose in an empty container, open the oil change valve (just a ball valve from Home Depot), and pushing the button to run the pump. All done in 3 minutes.
I never enjoyed changing the oil, now I genuinely do! Admittedly, it probably gets out less than the nifty hole in the transmission cover (depending on the tilt of the machine) but surely more than what I got previously. And it is so easy (did I mention fun?) that I have been known to just do two (or three) oil changes in a row, separated by running the machine for 10 minutes, to mix the new oil in. Which means I get nearly all the old oil out, and it only costs me a couple quarts oil.
Cost is about $80.- for the Indigo kit, the pump was about $20.-. Plus maybe another $20.- for a ball valve, an electrical switch, a few feet of hose and a couple hose clamps.