I’m not at all sure what you would use for a mister, so this example would use a SmartThings outlet plug that would turn on the outlet for a duration of ‘x’ minute(s) every hour and uses a virtual switch as the countdown timer for re-triggering the Automation. The virtual switch turn Off value must be longer than the outlet turn Off value. Essentially it should loop constantly.
Outlet is Off
Virtual switch is Off
Turn On Outlet and Auto Turn Off in "x’ minute(s).
Turn On Virtual switch and Auto Turn Off in 1 hour.
However, any Automation comes with risks because if the power goes out at any time, then who knows what condition the outlet would be in when power is restored, and even then I have no idea how this would kick off when power is restored. In fact, you’d need to toggle the power outlet to Off and toggle the virtual switch On/Off to even start the trigger in this Automation example. So, in case of power outages, I would think that you would need some sort of power outage sensor that could be used as the trigger for an Automation If power is restored to Then turn the outlet Off and turn the virtual switch On and then Off a few seconds later when power is restored to get this Automation example to trigger and start looping after power outages.
Don’t they make fish tank pumps or something else that can do this manually (mechanically) and is impervious to power outages and environmental conditions? I’d go to some place like Petco and ask.