Arducopter V3.4.6 includes a flight mode “AUTOTUNE” that enables an alternative method of tuning with a 6-channel RC receiver. The instructions should be updated to include this new method. It should explain: (1) how to engage AUTOTUNE using the flight mode; (2) how to complete AUTOTUNE using the flight mode; and (3) how to perform AUTOTUNE in increments for copters with low endurance.
Wiki improvements suggestions can be made in the Wiki GitHub: https://github.com/ArduPilot/ardupilot_wiki/issues Every page also has a link to it in the bottom. If you want to go further and help us, you can press the Edit button at the top and do the changes yourself - someone in our team will then review and merge them.
I’ll try to answer your questions now:
It is a flight mode, you switch to it just like you do for any other mode.
All instructions apply. Using the aux switch means that putting to high it enters Autotune flight mode, putting it down, it goes back to what the flight mode switch is set to. So while using the flight mode switch to enter autotune, you save in the same way you do with the aux switch: “If you are happy with the autotuned PID gains, leave the ch7/ch8 switch in the HIGH position, land and disarm to save the PIDs permanently.”, meaning that you land with the Autotune flight mode activated.
I’m not sure I fully understand what you mean here. Are you thinking of stopping autotune and continuing in a next flight? If that is it, I’m pretty sure that isn’t supported.