The very best I have ever seen is an automotive clearcoat from PPG. It is called "Flexed and Flat". With most automotive clears you have to add a flettening agent to get the degree of flatness that you want. With "Flexed and Flat", it is already flat. I have used this flat on a large F-86 which was painted with a combination of Testors Model Master paint and Chevron Perfect Paint. This clear gives an extremely nice coat to the paint. I have also used it some repaired sections on a Jet Model Products T-33. This is a sperior product which is fuelproof and WILL NOT YELLOW.

If you decide to use this clear, the trick is to use 1 part clear and 2 parts reducer. It sprays on in light coats and is not prone to runs.