... cask washing ...
Half the battle is getting them back in good time corked and pegged. As a small brewery you'll be in good steed to do so! When they are very fresh and not infested with flies they only take a minute or two.
I (used to ha ha ha) remove the furniture, clean the labels and outside with a pressure washer, then put them on an initial dirty water rinse which was a angle iron frame over a drain with a spray ball through the shive hole at the bottom. Whole thing was knocked up with spot welds, silicone pipe, pump, y strainer and an IBC taking rainwater off the guttering. Then pretty much the same thing, but over a big screwfix poly water trough containing chlorinated caustic. Finally they are stacked upside down and using a diesel powered pressure washer given 20-30 seconds of steam to rinse the caustic out and get them very hot. Hold at an angle to drain the last bit of water, knock in the key stone, part knock in the shive and stack ready to be filled. With a three head washer, stop valves and plenty of energy usually took most of the morning to get 80-90 done. Dwell time should be minimised, day or two. Approx build cost was £700 including the pumps, but these were surplus brewery pumps. Pressure washer was a couple of grand, but has other uses. Pretty much looked at lovely stainless versions and made the same thing out of polypipe and random junk?
I've known other brewers do the entire job with just a pressure washer and steam at the end? Also with no steam and PAA rinse to sanitise?
Personally (if cleanish) I'd clean the outside, remove the keystone and shive, place it on something shive down and stick a decent hose through the keystone so the rubbish can flush straight out the shive hole. Once mainly clear I'd inspect it with a torch through the keystone looking through the shive and if acceptable chuck a jug of PAA in there, shake it around, bang in fresh dipped furniture. You just need a bit of outside space. You'll eventually encounter problems, but you could fill with 2% caustic, seal up, leave overnight, roll occasionally and so on.
