Changng Transmission Fluid - need some hints

[Indian Falls]

How do you know your tube got to the bottom and you got all the oil?  Not for nuthin' but it is a mute point if the oil is changed every year in whatever way.  However I have been finding that in 20 years many of the things I'm doing to my boat are for the first time.  In that respect I'd rather pull the plug and let it drain for real.  Using any variety of pumps from the top does not give me that 100% feeling of completion.  But that's just me being a maintenance technician 25 plus years...

"Do it nice or do it twice" I always say.