Woodie explained how to do it on here once...
When youre done sanding the paint down, you take the sandpaper and sand it down with sandpaper. Once you have 2 cups of sand, you pour one cup into the defroster vent on the dashboard, and the other half into the gas tank, and start the car. This causes the shiny grains of sand to be kicked into the air to create a gold flake layer, dont worry its not harmful, because the harmful sand was ground down by the sandpaper.
Next step is to take the paper from the sandpaper, make a funnel of it, and insert it into the gas tank. Pour one bottle nail polish remover into the funnel to help dilude any slight imperfections in the sand, while forming a non-flammable seal over the fuel. It will be hard to see inside, so make sure you light a match or lighter to add light, and put your eye as close as you can.
The rest is simple to copy by looks