[VergeGTO]

Thanks for the tips. I'll just keep it basic, like you explained. ...or maybe get a tiny little brush and a surgeon's hand.

[xgoater]

I do it basically the way Lust4 does it but sometimes I will also use an old t-shirt pulled tightly over the end of a putty knife and with the rag just barely damp with thinner. I then rub it over the top of recessed letters. It has always given me clean edges and doesn't allow me to get inside the recessed painted area. You just need to not have the rag dripping wet and keep the rag pulled tight - you can double over the rag if you want a little more rag on the end of the blade. FWIW I wouldn't use a brush at all - too risky and sloppy.

[VergeGTO]

Hey excellent cleanup tip with the old shirt / putty knife - Thanks! ...and I was kidding about the brush, it'd be like playing that game old game "Operation"

[Greg Reid]

You can use a brush...I've done that kind of stuff with a small brush for years...you just don't worry about trying to stay inside the letters. Cleanup around the letters the same way you would clean up the overspray. The same way these guys described it above.
Your idea of the sponge would work too. I've even used a wooden kitchen match, a toothpick etc.
Lots of ways to skin a cat.