Looking for a solution to cleaning the external rubber pipes on the bags, paint is not an option.

grease and wax remover can be used or hot water and soap and tooth brush, not your partners tooth brush.
Allen

I was more worried about the inside of the bags than the outside. A few months ago I flushed out most of the gunge and rust from my supply of hopefully never to be used spares and refilled them with long life antifreeze.
Is that the best way to preserve them?

I believe so. I use 50/50 ethylene glycol longlife and demineralised water. Also use this on the car.
Be careful around the hose crimp on the bag, hoses tend to rot there or get brittle. Don't swing the bag by the hose.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.