Polishing + County ?? 
Easiest way to polish it would be to remove it, and either take it to someone who does polishing work, or have a go yourself. Almost impossible to do on the vehicle without risking damage to the surrounding paintwork I'd reckon.
Same goes for sealing it up IMO. Need to remove it, then give it a good degrease with thinners etc and spray with some clear. Trouble with that is its a working surface so the clear is going to get scratched off and you'll be back to where you started.
Maybe try some decent wax, but if the surface is rough I don't like your chances.
If I was mine and I was concerned about cosmetic issues (which I'm not
) I'd be removing and polishing then maybe a bit of wax if it was still not up to the required standard.
Steve
1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
1988 120 with rust and potential
1999 300tdi 130 single cab - "stock as bro"
2003 D2a Td5 - the boss's daily drive
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