hello rizo . beware of polish , made especially for the tole ( car ) it eats the varnish ( made to give back the shine to the old car bodies ) the wax is made for the wood , it is sticky ( it pate ) . We use soap, window cleaner. There are renovators or varnishes to do this; see the site "Thoman". For the chrome also, if really dull, there is the white stone, polishes that we find in silverware, see also on websites (is used those on my viola (pichotte and tuba, practiced in the harmony) the aspect is surprising a real mirror. The plastic, I will see of the acetone for good cleaning (glue grease yellow spots etc ....) then a varnishing. In current maintenance, soap or washes glass to preserve the varnish. Here, for what I can advise you, also see a luthier. Go to elbow grease and good cleaning rizo.