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?

Unfortunately when you can't get hold of things then you may need to stick to more traditional methods using materials you can get hold of.