When descending, options are basically these:
fixed line travel (next slowest)
If the terrain can be downclimbed or all or most team members, that should usually be your first choice. If some of the team can downclimb but some don’t want to, send down the climbers first, then rap or travel fixed line with the rest - don’t make everyone rappel.
What if the terrain is a loose and rocky, with a high chance of climber-induced rockfall? The conservative, (and slow) approach is to send down only one person at a time through the shooting gallery. However, it’s often just as safe to send down 2 or more people at the same time, and making sure they stay close together, ideally on the same contour. That way, any rocks kicked loose bound harmlessly away, and two (or more) can descend in the same time as one.
One other option is what's called “downleading”. The second to last person descending can place some gear and clip the rope to it, to partially protect the last person who downclimbs. It's covered in more detail at this tip here.