RE: Gas engine mess during breaking in, is this excessive?
Not that I know of. Straight Gas, like methanol, is not agressive like synthetic lubricant, nitro or paint thinner.
The best way to find out, is to use the cleaning agent in a small place, not seen, and check out.
I am not a big fan of film covering, just because most fuels wreck the seams and that beautiful finish goes down the drain.