Printed parts for multi instruments;

I have a part that uses two instruments/sounds and when I print it, I would like to NOT see the rests of the part not being played… is there a quick fix? It seems to work fine with percussion with no extra setup…

It depends a bit on how you are combining the instruments/parts.
Maybe you need the option Hide Empty Staves, which you find in Layout Options - Vertical Spacing - Staff Visibility.
Or is it one player ‘holding’ (switching between) several instruments? Dorico will handle that automatically, if the music is entered on different staves for each instrument, and you allow instrument changes in the Layout.
If the non-playing player is silent in an entire flow, just un-assign the player from that flow altogether in Setup Mode, then they won’t have their own staff.