I see that the GC50 is used before laying up the carbon on high gloss parts. But what do you use to apply it? I think the easy composites gelcoat spraying cup gun is a bit expensive, is there other ways to apply it and still get a high gloss result? Can for example a plastic spray bottle be used?

Bah, where's the sense of adventure Dravis!?

Large parts are no more difficult to spray than small parts, in-fact in some cases a bonnet is much easier than a smaller more complex part. Of course, you wouldn't want to do it with a rattle can, you'd need a proper spray gun. But still... The only times I've ever run into trouble with my work is when I've got other people involved. I'm still paying for the last job I got a professional spray painter to do for me. Even highly reputed professionals cut corners sometimes. These days I do everything myself, to make sure it's done properly.