This is far from automatic, but it is the only way I know of to get NWC to strum natural-sounding guitar chords. Go to this link to the NWC Scriptorium and unzip the file
http://nwc-scriptorium.org/ftp/helpful/guitarstrum.zipbesure to read the Read Me file first so the files make sense when you construct a guitar chord part with them. I am a guitarist myself and I put a lot of time and trial and error into these files to make them sound like the guitarist who isn't really there.