Sounds like a fun prank, but before you spray anything on a human body I’d want to know the exact composition and safety data. To get an “invisible” effect you’d need a substance that matches the refractive index of skin—probably a transparent polymer or a thin layer of something like a diluted epoxy resin or a silicone that’s clear and non‑volatile. But most of those contain solvents that are flammable, irritating or even toxic. I’d suggest you run a small test on a piece of fabric first, check the vapor pressure, and be sure you have proper ventilation and PPE. If you’re really set on a quick spray, a water‑based colloidal suspension with a refractive index close to 1.4 might work, but it’ll only last a few minutes before it dries or washes off. And remember, any off‑label use of chemicals on skin can have unpredictable effects. If you want the recipe, give me the exact chemicals and concentrations and we can evaluate the risks.