I wouldn't think that corn syrup would yeild much of a traditional flavor, but it will ferment. As for the amount to use, it depends on the size of wash and the type of yeast you are going to be using.
The corn syrup should have the grams of sugar per serving listed on the container. 454 grams is one pound if memory serves, so I would use enough corn syrup to provide about 800 grams ( or 1.75 lbs.) of sugar per gallon of wash if not using other sugars. Depending on the type of yeast you are using you may need more or less.
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