I would get a small sponge and cut it into the size square you want, then use diluted (with alcohol) airbrush color to sponge the squares on.
Theresa 
go to Just Fabulous Pastries (in San Diego). There are 2 on their site. One is called Argyle and the other is the Dancing Couple. If you call them or email them and they are not BZ they may help. Don't be timid!
Hi All!
THIS IS SO FUNNY , I JUST HAD THIS DILEMMA THIS PAST WEEKEND. I DECIDED TO CUT A TEMPLATE FROM A CARDBOARD. I MEASURED IT AND CUT A STRIP ABOUT A 1/2" THICK EVERY 3/4-1". THEN I TOOK MY SPRAY MIST,OR AIRBRUSH IF YOU HAVE IT. FIRST I TOOK THE TEMPLATE AND SPRAYED MY LINES HORIZONTALLY THENK CHANGED THE TEMPLATE TO ITS SIDE AND SPRAYED VERTICAL. IT TURNED OUT AWSOME!!!! IT EVEN HAD THE DARKER AREAS WHERE THE SPRAY OVERLAPPED ITSELF. IT WAS A TWO LAYER 12" HEX. THE WHOLE TECH. TOOK ABOUT 10 MINS. THE CLIENT JUST LOVED IT.
GOOD LUCK, HOPE THIS HELPS.
DAWN
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