Best Method - Duck Everything Except One Part

[struknes]

I want to make everything momentarily duck except a certain guitar part. Is there a faster method than automating the volume down on everything except it?

[Da hand]

Method 1. Group all the tracks, except the guitar track. Automate the group as you like.
Method 2. Create a new audio track - let's call it "Bus 1". Send the audio outputs of all the tracks, except the guitar track, to Bus 1. Automate Bus 1 as you like.