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Yep. The method of disconnecting the outbound line to the cooler has been my preferred method for long time. I tow a 5 ton boat with my truck, so the 20 qts of fluid gets changed every season. I will note, however; I designed a beer bong with a r&r'd coat hanger hook about 6 ft long clear vinyl tube and a nipple to add fluid in the side plug. I hang it from a step ladder near the car, so I can see it from all angles. (I use a similar setup as a one man brake bleeder, which is very very effective). I also use a mirror to monitor the plug hole. I keep a catch pan underneath. no muss no fuss.

Quicksilver Vert 01

Unless you're exceeding the maximum tow rating, or driving 50k miles a year in your truck, you're probably wasting your money by doing fluid changes every season.

Quality synthetic transmission fluids are designed for 50k mile change intervals under severe conditions, which would include your truck, if it's maximum tow rating is not exceeded.

MikaN

What if you just leave the filter off and connect the vinyl hose to the filter input.
Huge drain pan under the transmission and run the car.
No need to disconnect any cooler line.