After watching several videos about brighten up your old retro gear I tried the method on my SNES (see 8-Bit Guy cleaning an old computer). Unfortunately with mixed results.
Instead of mixing the retr0bright mixture I’ve bought cream oxide with 12% hydrogen peroxide. Since its a cream it sticks fine on the SNES case. To prevent it from drying I wrapped it in transparent polythene foil and left it a few hours in direct sunlight.

After cleaning the case looked brighter but you can see some flow marks now. That was not seen in all the videos I’ve watched 🙂

I’ve tried the process several times and currently its again in the sun but I guess the marks will stay.
Please let me know if anyone has some tips to get a nice and bright SNES case without marks.