Well, you said "the best way" which really puts cost aside in favor of results. Doing a full restoration of the playfield with restoration of artwork, releveling inserts and professional clearcoating would be the best. But, in this case, the cost of fixing the playfield back to better than new will cost more than the game is worth.

There are other options such as using some acrylic paints, and matching to the surrounding areas as best as you can, and doing the touch-ups yourself. Then either clearcoating yourself or simply applying mylar over the affected areas.

Really depends on how much you want to spend and how perfect the game has to be for you to enjoy it. I'm in the touch-up and mylar camp, but that's not really 'the best' option for most people.