Best way to clean a sign?

[index]

I've got this sign from a thrift store, and as you can see, it's quite dirty.



I don't know where to put this thread, so I've put it here, in off topic.
Anyways, what's the best way to go about washing this sign? I've already removed the less tough stains with a rag and some soap solution, which cleaned it up a bit, but not too much. Should I use a special solution, get someone to power wash it for me, etc.?

[Max Rockatansky]

Armour All Car Detail touch up spray and microfibers are a good way to lift surface dirt with it not being abrasive on the vinyl.  I use said spray on my Challenger which has a bunch of vinyl striping on it and it works really well, the microfibers won't leave surface scratches either.