how?

If you have a look in our links here you will find details of a couple of firms which specialise in refurbishing alloys.

And some of the ChipsAway chaps do it too. My local VW dealer uses ChipsAway to prep used cars for resale.

........and is it likely to be worth the outlay when selling a 2nd hand car?

... That's a million dollar question !

Depends how bad the alloys are and depends if you are trading in or selling privately.

If trading in and not bad damage it won't make any difference. If private sale and everything else about the car is perfect, then yes. Wicked wheels (mobile) did a good job on my Impreza.

Rob