Can you imagine all the naysayers Eugene probably had to go through? I think probably every advancement in the storied history of that rifle, like all others, probably had its vocal detractors. Don't get too discouraged.
I do agree another video is needed. Something that shows what the thing really does. Show how one normally clears the malfunction, then show how one clears the malfunction with your device. Show the weapon firing, show the bolt locking back on an empty mag, then show people that you can still manipulate it like normal.
As for finishes, I think something like Duracoat would work well. It seems to be easily applied, durable, and available in a large selection of colors. I would recommend matte black, flat dark earth, olive drab, and maybe a charcoal gray.
It might actually help if once you got things up and running, you have a few of these away for testing. In the right hands, with the right reviews, this thing could really catch on. Have you showed this off at AR-15.com?