For your metronome question:
-Go from clicking every beat to every other, to only beat one, etc
-Use Tonal Energy, it has settings to randomly drop beats, increase the percentage over time
-Use a Harmony Director or another met with a quick volume control, start the band with the met then drop the volume to zero. Bring the volume back up after a bar or two. Using the volume instead of turning the met on and off keeps the time going silently

The suggestions below about listening the motor are good in pieces that have that. My college professor referred to "pulse givers" and "pulse takers" - know which one you are at any given point in the music.