Firstly, welcome back John - even Johnny has been missing you! As for the symbols, if the grooves are still deep enough paint over the whole lot with a white cellulose, really whack it on wait for it to go tacky, then with a piece of cloth soaked in thinners wipe over untill the paint is removed from the flats but left in the grooves of the symbols, dont use a fluffy cloth though as you will get bits of fluff left in the symbols, and dont use a towelling type cloth this will lift the paint out of the grooves, old shirts are a good fabric source (nice and flat and if they have been washed enough no bits of fluff) If the grooves of the symbols are not that deep, use the same method as above but let the paint go off and then remove it from the flats with a fine wet and dry, finish off with your cutting compound of chioce hey presto shiny black plastic and whiter than white symbols.
Cheers
Al