I wasn’t talking about palm muting, though this can also be used if desired.
I was talking about regular string muting which is a part of normal playing. i.e. how you stop unplayed strings from ringing out and how you bring a played string to rest. So a combination of having left-hand fingers resting lightly on unplayed strings and lifting a finger from a fretted note cleanly whilst quickly putting down other fingers lightly on that string to prevent any note-off noise. Then in the right hand, a combination of thumb/finger anchoring on unplayed strings and the Gary Willis right-hand finger muting technique whereby after you’ve plucked a note with one finger, the alternate finger is placed on that string to mute the note.
Using all these things together where needed does vastly improve how the FI plays. Not only that, they are all useful tools in normal playing to help control note length, articulation and clean playing (no unwanted notes ringing out).