Hey man, thanks for sending over pictures! It's a lot easier to see what you mean about the tail lights. Buffing doesn't make too much sense if the milky/foggy part is on the inside!
I'm assuming they got this way from moisture getting inside somehow over the years. Unfortunately, I don't have any tips for you other than attempting to disassemble the lens and buff it. However, since you've been a very active MF member over the last year and seem to always provide your input to help other members when possible, I wouldn't mind helping you out with a new set. Even though these Raxiom tail lights are well past their warranty.
Send me another PM with your Last name and shipping address. I'll ship you out a free set this evening!
Lastly, I'm actually not sure what extra harness you received with your package. It doesn't look too familiar to me, but it's also a little hard to see the connections in the pictures. Especially of what looks to be a switch? Can you provide a closer shot of that for me?