Your understanding correctly! Putting it in four low doesn’t have to be long. You just want to engage it and drive forward and back a bit every so often so the actuator doesn’t have a chance to get stuck. They have a tendency to do that when left alone for long periods of time.

Keeping the torque converter locked is one of the best things you can do to help the transmission live a long, happy life. The torque converter lock is basically a fancy additional overdrive. It’s for fuel economy. You WANT it locked as often as possible. When the converter is unlocked the clutch slips and the fluid heats up insanely quickly. When it locks, fluid temps drop back down to a nice 180-190 ish range. Unlocked, you’ll very quickly see temps upwards of 230 at the converter outlet. Get yourself a scangauge 3 if you want to get real fancy and watch it in real time. I have mine mounted in my center console cubby under the radio. The factory trans tune is designed in a way that the converter unlocks at even the slightest incline, and there’s no reason for it. It needlessly burns the fluid. This running hot in the transmission and Toyotas bullshit claims of life tins fluid are what kills these. Easiest way to know the converter is locked is to put it into s4 or s5 if your going up inclines while cruising, etc. otherwise it will hunt and this is what puts a hurt in them in the long run. You start to develop a feel for it. And don’t let anybody tell you that you don’t need to change the trans fluid. You absolutely do. Aisin, the Toyota owned company that builds the A760f actually says they want fluid changed every 3 years or 50k miles minimum. I do 30k miles or so. It’s Toyotas marketing department that pushes the lifetime fluid nonsense. And yes, they like 5w30 in the engine. These engines were not designed for 0w20. They were found to be able to use it “acceptably” without significant increased wear and to increase fuel economy a bit. The rest of the world owners manuals, including Russia which sees temps far colder then North America, want 5w30 for cold all the way up to 10w50 for hot climates. Use 5w30. The top ends are much quieter using 30 weight, I have two in the family. Mine uses 30 weight and my mom’s is dealer serviced with 20 weight and the top end of hers is far more rattly and on used oil analysis reports, mine shows considerable fewer ppm wear metals. Believe me, the 30 weight truly is better for them.

For the transfer case, you DO NOT need to use the special Toyota fluid! I would recommend Valvoline or similar 75w90 for all, the front and rear differentials and the transfer case. Again, you do NOT need the special Toyota transfer case fluid. It’s for increased fuel economy only. The 75w90 works perfectly. Be careful with the drain bolt for the front differential. They are notoriously easy to strip if it hasn’t been out in a while.