How to clean leather hat?

[AEBL]

Sorry if this is not the right place - but I'm sure someone here knows the right answer:

I got a request for an "aviator" (winter) leather hat, with a shearling liner of some sort (perhaps even cloth). I know when I use hats I wind up using them outside, working, and my head winds up getting hot and sweaty.
My hats are usually something I can toss in the washing machine, but I was asked to make a leather one.
How on earth would they clean it? Would it make sense to have a removable liner or something?

[fredk]

Very gently hand wash. Don't soak it. Use animal friendly, ie dog, shampoo on the furry bit. A mild dish-washing liquid soap on the leather. Sponge wash with very warm, not hot, water. Sponge dry, turn inside-out to finish the drying by warm air 

[AEBL]

Thanks