A friend of mine had an 18' Hondo that was a silver metal flake. He sanded 90% of it down and with 220 grit dry and then used a Primer called Feather Fill. He then sanded that with 400 grit wet and then applied DP40 Primer in black. Light gray primers are translucent and might show transitions in any bodywork you may have done. After applying the DP40 primer he wet sanded that in 800 wet and then applied his basecoat. From there he flamed it and then cleared it. All products were PPG. You can get them at Automotive Paint supply stores. Sometimes you can call one of your local bodyshops and find out where a local PPG distributor is near you.