Differing volumes on a stave.

Using Musescore 2.3.1. Writing music for handbells. I have the soprano and alto parts on the treble stave, but in places I need the main melody to be in the alto part, and the soprano part to play quietly above. How do I get this to happen, as I initially produce an MP3 version for everyone to hear first.

Also, does anyone know of an app that I can use to help sort the arranging of the bells between the different ringers, allowing time for each ringer to put one bell down and pick up the next bell in readiness, always allowing for the speed of the music. We always have 2 bells each, and often three or four bells, so changing bells can be tricky.