While working for a Robinson dealer I was told by the Chief Engineer of an experience he had when it became impossible to refit the perspex into an R22 properly as the sealant wouldn't adhere to it. Investigation revealed that the owner had been using "Mr. Sheen" to clean the perspex & it had impregnated the bubble with chemicals which the sealant couldn't adhere to - therefore a new bubble was required & I'll let the reader imagine the backflips performed by the owner when he saw the quote! I'd suggest a plastic "squirty bottle" with a mild detergent & water & avoid the commercial glass cleaners. As for fogging up inside, I NEVER fly Robinsons in rainy conditions with the pilots door on as the bubble can become completely obscured in certain conditions within a millisecond. Having said that I don't have to deal with low ambient temperatures so I'll let someone else comment on the best practice there. Call me a sook but I'd rather be wet than dead.