There's lots of good advice here, so let me offer a (slightly) contrarian view.
First, there's
thrust, and then there's
thrust. I've worked in
thrust stages where maybe 75% of the audience has a more-or-less front view, and the shows are played more-or-less forward. In these cases I still use a 4-point
system, with a straight front (6:00), sides somewhat more saturated and saturated backs. So not everyone's getting exactly the same picture, but generally the
face is in the frontlight, toned by the side and the
stage is toned from the back. People on the extreme sides get more saturated light on part of the
face when an actor is facing them, but that doesn't bother me.
I also typically do high sides (from a steep angle) with a soft breakup in R53 or other very pale color. This adds definition to faces and allows you to be more saturated in your area lights, as you perceive the pale highlights as white light, even if it's not hitting 100% of the
face.
And I'll do other toning washing and whatnot on top of that. This is for musicals, and gives me a lot of flexibility in looks. The problem with doing a four-point pale
system is that you use up so much equipment just to create a basic look. If you have it, great. I think my
system works in slightly under-resourced venues.
Since this is a festival you may also consider whether the shows will be playing the
thrust, or were they blocked on
proscenium stages and will be playing all front? You may not need to worry about the
thrust all that much. (But better safe than sorry I guess.)