You should only mist the medium there in not the leaves themselves or it will never work on rooting just from my own experience. I usually do it twice a day, but if it looks really dry I would do it more then twice.
Whereas I would say to mist the leaves, and never the medium. An oversaturated medium will NEVER root (people who clone hydro/aero have tons of oxygen in their "medium")
I usually mist twice (lights on and an hour or two before lights off) a day for first 3 days, and then only when drooping starts. Not sure if you are venting or propping a dome or whatever, but I religiously open the vents at day 3 for 3 hours and if none of the cuttings droop, it stays open for a day. If some droop shows then, I mist to correct and leave vents open. By day 7 (days 3-7 vents open) you know damn well who is going to live and who is going to die.
Some people argue misting 4 times a day, but I find that to be overkill.
Temp is more important IMO, I don't use heat mats unless the ambient room temp is below 65, I have a vented area that sits around 85F with lights on, took cuttings 2 days ago and I'll be damned if they don't look like they are still on the plant....pretty sure they even grew a little bit in 2 days......