Is there a way to "Gray Out" Optional Notes while Keeping Others on the Same Staff in Black??

I have transcribed some vocal choral parts that are normally spread across four separate staffs in a system into a piano part on a grand staff. My purpose in doing so is to assist make it easy for a pianist during choir rehearsals to easily read & play all choral parts at once. (These choral parts would otherwise be quite difficult -- partly due to the vertical spacing that must be read at once, but also because the tenor part was originally written on a treble staff to be sung an octave lower than written can be confusing to read simulateously with two treble staffs above it for soprano & alto voices & a bass staff below it for the bass part.) My solution was to transcribe all the vocal parts onto a grand staff, as mentioned, but with that to also write the tenor part on the bass staff along with the bass part. Please Note: I have chosen to fill in measures where the voices do NOT sing with some accompaniment, in lieu of including multiple measures in some spots that are simply have whole-measure rests. This is to allow the pianist during rehearsals to play partial accompaniment during those measures -- to train the singers as to what they can expect to hearing when no one should be singing. However, when another accompanist is present to play the "true" accompaniment on an organ, the pianist's partial accompaniment then becomes optional or unnecessary. So..., I am hoping that there is a way to SELECTIVELY gray out music on parts of a grand staff, so that only the vocal parts appear in normal print. Is this possible & how would I do this?? Thanks so much! Nolan W. Cook