to do powdercoating right you need to blast and then ecth with a converson prosess phosphating being one of these, all of whitch will remove the look you are after. you could just clean with a wax and grease remover and then coat .your powder finish is not going to be as durable without the proper pretreatment but probley tougher than anything you can spray from a can.
their are serval clear powercoateing avaible from very glossey to satin depending on the brand of powder from very slick to ruff surface texture are avable you should talk with a local coater.you may want to use an oil finish.