The first photo is after cleaning with Windex and a 'fast cut' polish compound using a pneumatic buffing wheel.
Not a lot of change to the fading in the Cobalt. But I thought it was worth a shot.
As you can see, the sign appears to have spent some time horizontal with some 2 by 4's laid across it.
The second photo is after cleaning with ZAP! and a red Scotch-Bright pad.
I didn't try to scratch the surface with the Scotch-Bright pad, just a bit of pressure to clean up gunk and work the ZAP! into the hazy porcelain.
This removed a lot of the hazing. I might do this step and the next again before the new neon is installed.
Final photo is with the RH side coated with Feed-N-Wax.
As you can see, this really evens out the Cobalt and richens up the color.
The Feed-N-Wax will usually last about 4-6 months - then it needs to be reapplied.
But the sign looks much better even without the Feed-N-Wax.
Later . . .