Wthout a humidity issue then it may not be necessary, but I sure feel confident with the glasses I have done, so if it's valuable to you (as I'm sure it is) then worth doing, because when the glass is in good condition it's simple.

The product to find is Krylon Triple Thick - no idea who has this these days, in fact if anyne knows where it can be sourced can you post here to let others know?

Here's the step by step.   http://www.pinrepair.com/restore/index1.htm#bg  The only bit of concern is covering the score display windows, otherwise it's just spray away!