Butyrate goes over butyrate very well. It pretty much does NOT go over anything else. Nor anything over it either. Nitrate dope will accept many other finishes over it, but butyrate does not.

How much fuel proofing do you need? Quite a few of the water based clear polyurethanes are fuel proof insomuch as you can quickly wipe off a spill without any damage, but if you try to scrub the plane with steel wool soaked in fuel, well yeah, it is not fuel proof. All things are relative.