At the repair bench, we use Lacquer Thinner on the vinyl cords as well as the bumpers. Takes off years of grime. However, do NOT use it on plastic. For plastic, use rubbing alcohol. The, we use Vac Polish on the entire thing, let it dry 10 minutes, then buff it off. Shines like a new machine.
I use denatured alcohol...same thing I use on tape heads....bought at a paint or good hardware/box store. Works great, but I don't use it as a maintenance thing for vacs...just cleaning up something old or battle weary. There's times though that denatured alcohol is not strong enough. From there I go to MEK......but it's really toxic and melts plastic very easily. Usually, I have to buff the plastic afterward to remove the streak marks from the pad or rags I used. It's only as a last ditch effort.