Use both sides, they aren't 'side specific'.
Odd things too aren't they, when you are using them they feel like a new chamois leather.
Don't wrry about the few marks that may still be on them when they come out tof the washing machine, you aren't wearing them for Sunday best, you're cleaning windows with them!
Beware conditioner though
Actually, I've never liked using conditioner with scrims either, better off without it
Ian