I dry mine on a maiden at the side of the open fire lol! They dry (inc bamboo inserts) in 12-24hours
(depending on if i remember to turn them lol)
Tho since we've lost the coal shovel under the 8+" of snow we cant get coal so the fire isnt lit
so i put yesterdays lot upstairs on a maiden in our bedroom, think theyre just about dry now, so thats about 36hours.
I dont see any harm in tumbling, when we had builders in making lots of dust i tumbled mine completely (on low) to get them out of the way or they would have gotten dirty... there were no problems except my HO BV got a bit 'plucked' looking as someone else has once mentioned on here. My other BV nappies like HL etc were fine so maybe its just that type of BV she uses.