I have a '65 Chevelle with a black convertible top. The top is in good condition, with no holes or rips, but has a dull look to it. Any suggestions on how to brighten it up without damaging it? I thought about using vinyl cleaner or Armor All, but have concerns about messing up the vinyl. I have the original GM folding top manual which recommends washing with a soft cloth and mild soap. That didn't produce the results I was hoping for.