If it is going to be a race body, you can always just paint the outside of the front end/nose on the car and not worry about masking the inside. The other option would be to use decals to cover any problem areas.

Unless you are painting a shelf queen body, all VTA bodies are going to eventually have their front end destroyed. Unless you enjoy having a perfectly painted race body (many people do), don't sweat details that won't be seen from the driver's stand.

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The best use of painting the outside is on bodies like the Pegasus Mustang. It is much easier to paint the front grill from the outside of the body than the inside. If you are painting the grill black on the outside it will end up with a matte appearance, which does look good.