I would just get a gallon size bottle of distilled water, add 1 oz. (a shot glass full) of the N-914 to the distilled water bottle, put the cap on the bottle, shave well, and add a label that says "N-914 Quick Detailer" or "Rinseless Wash" as the case may be. Then fill your spray bottles from the pre-mixed gallon container. Shake before you fill your spray bottles. Not much calculation, and easy to see the amount left.
Kostas
If I did it that way I'd have 10 - 1 gallon jugs to worry about storing. 1 ounce is 2 tablespoons or about 30 milliliters. I don't know about you but my shot glass is 16 ounces lol
No but seriously I just keep a few measuring spoons with my detailing stuff. That way I only have to buy 1 or 2 gallons of distilled water at a time. But I also only work on 1 car so that makes a difference.