Instrument Insertion Mid-Piece and MIDI

Is there a way to insert an instrument part at a particular measure/instance in the piece rather than have the instrument present from the very beginning? This will remove the fourteen or so measures of rests usually present up until its entry, and will solve many of my problems with having to format the existing parts to accommodate solo parts in a choral piece I am working on. Sibelius and Finale have this feature, though both are very costly, and I prefer MuseScore anyway. I am sure that this feature exists somewhere, but I cannot seem to find it. Would you kindly point me to it?

I would also like to know if there is any possibility of adapting the function/settings of the MIDI Playback for the sake of improvement in any way; it seems to be, in my opinion, a tad lackluster in quality.