I agree on using the automation. I did it to clean up a pretty half assed acoustic experiment I did a year ago. It was just supposed to be a demo, but I ended up having a friend play a solo on it for kicks and needed to increase the audio quality.
The sliding noise was not that loud in the room, but then I started doing lots of eq, reverb, processing etc and the noises became much more noticeable. So I automated the the volume down on the chord changes so I could still hear the slide noises, but not be bothered by them.
What I really should have done was get a better recording at the source so that I would not have needed to process it so much later.