paint

If i was to grab a clear shell and paint the underside a matt black, how easy would it be for me to use hobby tools or knives to scratch away parts of the paintwork to expose gaps? Im after a weathered look and would like to add metal rivots or deep scratches by adding a second coat of metallic...

I got tired of the original green and silver bodies, did an outside repaint on one using Kryolon dessert tan then ordered a new clear body to paint from the underside, red with racing stripes!