It'd probably be very hard to determine the ideal area for application, but in general, try to spread it enough to where there aren't any "puddles," or places that you can actually see liquid rather than your skin just being shiny from the moisture.
No idea on if it's possible to spread it TOO thin, but for most of our intents and purposes, it's probably not that big of an issue. Plus, if you're trying to apply like one spray of
S1+ to your entire chest, the liquid probably wouldn't even spread out that much.
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