[Boatanchors] Removing Cigarette Tar from painted 19" panel

[Howie WA3MCK]

Gang,

I have a surplus home brew 40 meter receiver with a 19" steel front panel
painted light grey I acquired at a local hamfest last month.

 It's in pretty bad shape and will need to be gutted and rebuilt; but it
was worth 5 bucks!

The front panel is covered in cigarette tar/smoke.

I've tried alcohol based glass cleaner with mediocre results.
Even tried that "scrubbing bubbles" stuff... also mediocre results.

Recommendations?
Suggestions?

Tnx es 73 de Howie WA3MCK