Sticking brake calipers have nothing to do with brake fluid and everythign to do with the rails they slide on.
My 93 Pace Arrow is on an Oshkosh Chassis and the front calipers WILL stick if left unused for an extended period of time. First drive of the season I will do short stops in both forward & reverse. I then take her out on the road for a short 1 - 2 mile drive & feel for a tight pedal when stopping.
If they do get stuck I can pull the calipers and clean/lube the rails with a LIGHT coat of hi-temp lubricant, e.g. exhaust brake lube.
