Cant advise on best way to clean I have used the hat cleaner which seemed best.
I can, however tell you a horror story. I kept my skull cap on a hook above my box in an old tack room
I grabbed it one day and hopped on the horse in a hurry as I had a chance to whizz round a XC course before the fences were rewired. I felt an itchy wriggly feeling as I warmed up so I stopped and took my hat off - Investigations found a whole herd (is that the correct word) of woodlice had made their home in the lining yuk!!