The KBS Clear Diamond finish is NOT fuel proof. I tried it, the aerosol version, and raw fuel ate it up. I contacted the manufacturer via email. The response I got was that the Clear Diamond product was not designed to be resistant to chemicals. You have to use their two-part product for that.
I don't know of any one-part product that will resist nitro or methanol. The way I see it, the KBS Diamond Clear might be a bit better than clear dope. As long as you avoid splashing raw fuel on it, you should be OK. And, I have no idea how well it resists yellowing over time.