I don't have experience with that specific product, but I have now used two other decal products, and the question I'm left with is why anyone worries about fuel-proofing decals? So far I haven't needed to. Of course, I have not put any on the fuselage near the engine, but the ones I have put on the wing have come in contact with the blow-off from the engine, which is pretty much all castor anyway, and it cleans right off with no damage to the decal at all. I use windex to clean the wing, and again, no decal degradation. In fact, for the most part, the decals are out of the "engine-fuel zone", and don't actually come in contact with fuel from the engine or elsewhere at all.
As for how to go about fuel-proofing decals that need it, from what I've heard, whatever you use, you would need to mist on the first coat or two VERY lightly, to avoid melting the decal, but after that point a heavier coat or two would be fine. I've read this in reference to clear dope as well as other clear finishes. Of course, the best thing would be to test one or more products in advance... (and then let us know the results, of course!)