in general what is meant by 'spraying a dragon' is to lightly mist the dragon's back so it is like a light rain to encourage them to drink or to help with shedding. However, most dragons don't like to be misted from my experience so I find its just easier to soak them for shedding problems and if they look dehydrated.
Eye droppers or needless syringes can be used to drop water on a dragon's lip to encourage them to drink as well.
Misting their salad also increases the amount of water they can take in as well.
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PHLdyPayne