I'm planning to do mine like this:
- dry sand it with 1000 grit papers
- wash it clean
- apply a layer of hard clearcoat (I don't know what it is, will have to ask my friend since he suggested me this)
- let the clearcoat fully dry then wet sand it with 2000 grit papers
- wash it clean then apply another layer of hard clearcoat
- then finally sand it more with 2000 grit papers as needed
Actually this is how my friend done with his PS3 glossy casing, the result looks great, non-glossy from the look of it but still allow you to clean easily, sanded (although very fine) surface tends to hold onto dirt, dust, stain...
Please update you progress, BlackWidow is a very good "cheap" keyboard but the glossy finish is a deal breaker.