Adding new instruments partway through

version 0.9.5, Windows XP

I'm using MuseScore to upgrade our choir director's compositions from photocopied chickenscratch to readable music. The piece I'm working on now starts with a solo (which, by the way, I don't see as an option for when adding voices, so I have it labeled as "voice"), and then slowly adds in other voices.
Since I was only getting one line per page when I had all the voices present, I would really like to just have the solo at first, and then slowly add in the Altos, then the Sopranos, then the rest of the choir. When the solo's not singing, I'd like it to disappear. Is this possible?
Thank you!