You may notice once the panel is dry the engraved black areas look chalky or dull in appearance. This can be fixed in one of two ways. 1) 3-in-one oil 2) Clear Coat Spray
It all depends on how you want to finish your panel. I chose the first since the client did not want the panels clear coated but left raw.
You will want to follow the directions on the can of spray when clear coating a panel applying nice thin layers holding the nozzle no closer than 10" from the material and spraying in nice even flowing strokes from side to side.
When applying an oil coat put a dab of oil on each of the engraved areas (you can add more if needed). Rub the oil into the metal and over the engraving. You will need to coat the entire front of the panel with the oil since this process will most likely change the appearance of the metal to look more like a light gun metal.
Let the oil dry nearly completely... it will get a little tacky to the touch. Roughly 10 mins.
Take a clean rag or cheese cloth and buff the panel removing any excess oil.