What do I reset after the change? Do I start a new session after every adjustment?
Every time you change anything you should start a new session.
First runs you'll be looking at air pressure. Did you need to add or remove air pressure? Reset the session until you get a green on air pressure.
Once that's green, then you move to volume spacers. If you need to change those at all, you need to do the entire compression ratio setup procedure again and start a new session.
Each time you change volume spacers, you MUST do the compression ratio setup procedure and start a new session.
Make sure you put the same air pressure in that got you to the green air pressure setting too.
You might notice the air pressure isn't green anymore after you change volume spacers, so you may need to start over with air pressure again.
When you've finally gotten green on air pressure and volume spacers, start a new session and keep moving down the line, starting a new session each time you make any adjustment to compression or rebound, even if it's just one click. Although I recommend following the guide when adjusting compression and rebound and going at least 2 clicks so you can work your way to the correct setting.
Also, you should have at least two profiles created and stored. One for your fork and one for your shock (if you have one).
Each of these will have a different compression ratio, which is most important, and other details.
When you switch from fork to shock, upload the shock profile so you're working with the correct compression ratio.
When you move it back to the fork, upload the fork profile so you have the correct compression ratio to start with.