How to clean speaker grilles

Secure a Swiffer cloth to your vacuum attachment and go over the grill with that from the front side. The vacuum will be able to draw through the cloth and the dirt will attach to the cloth. This will also prevent tearing the cloth with sharp plastic edges on the attachment. The compressed air idea works just as well and it's a lot easier.

Best way is to remove the grill from the speakers an then apply an upholstery cleaner (foam in can) dedicated for seats car and let it dry slowly, i use it to clean once a year the grills of my Parsifal Ovation. Your grills will appear like new one with a very good smell.

I use to use a lint brush, the kind that feels like velvet with little grooves running through it. The handle swivels so you can change directions. My current speakers do not use grill covers. I use to own a several pairs of Dynaudio speakers that had magnetic grill covers. Worked great!

Yeah, just vacuum them. I do it every three years or so.