Bibby,

This problem is not new. Many paints are not fuel proof as you know. The Lustercote clear suggestion works on the acrylic but not on the enamel. So, here's a suggestion: Buy some clear acrylic to spray over the enamel. After that you should be able to spray the clear Lustercote. Also, if the enamels are dark colors you can use a clear polyurethane, which is fuel proof. In fact you could probably use clear polyurethane over both paints. Be aware that a slight darkening of light colors will occur. The only caution is that any clear coat will wear in places handled and rubbed which will then expose the paint underneath to fuel damage. Good luck.

Gerry