"How often do your skimmers need to be cleaned in order to keep it working reasonably well."
ALL skimmers need routine cleaning to maintain efficient skimming. I'd say at least once/week. Any build-up will quickily reduce the ability of foam to rise. Slight adjustments are needed at this point to keep it skimming.
"Details about the cleaning (riser tube, collection cup or a complete cleaning."
Barr skimmers (btw, although they can be run internal, prefered method is external) are designed to easly disassemble...just a twist of the neck and the riser/collection cup comes off...other parts are finger tightened nylon bolts. Rinse well. Collection cup drains to remote collection.
"How difficult is it to dial in your skimmer"
Not at all..."dial-in" is Instant.
Three adjustments: Air low, water flow, water level. I maintain about 40 SCFH with a john guest fitting while monitoring the air flow meter; leave my pump maxed out; adjust level in the main chamber with a ball valve on the outflow to about 1-2" below the riser. Turn it on and within minutes, you can get wet or dry foam. Yes...it IS instant!
"Does adding supplements/food ect. Make the skimmer go nuts."
I find that adding food (at least what I feed), putting my hands in the tank, etc... has the opposite affect...breaks down the foam head. No worries, within 30'-60' she's foaming again. Some chemicals I've added have caused it to "go nuts".
"Have your skimmers over flowed leaked ect."
Beckett skimmers are masters of the overflow!

Collection needs to be equiped with an auto-shut off (actually, the shut off simply puts back-preasure on the air input decreasing air flow and shutting down the head).
HTH