If you are using the Acrylic XF-16 I would use a bigger tip. The metallic particles are pretty big in that stuff. Also try some of Tamiya's retarder for the acrylics they will spray better and have less dry tip problems.
A thick bot out of scale gloss coating of 2K clear is probably the only safe bet. You might do it by gluing all decals down with Future or a white PVA glue like Krystal Clear by Microsol.
Your doing a great job. Allot of kits and builders omit the fuel tanks on mid-engine type cars. Yours look great. What gold are using for the suspension bits?
The 24 hrs of Spa starts at 10:30 AM EST Saturday. It's a grat race on a great track. The Good smile racing Mercedes AMG GT is on the pole. There are 72 cars.
Live Stream here from Motorsport.com SPA 24
I really like this Rowe Racing Porsche 911