I have a wedding cake to airbrush gold. A three tier. I have just practised with my airbrush and I am happy with the result but would you spray glaze over it to prevent the colour coming off should it be touched. I just touched with my finger and the gold came off leaving a large white mark.
That's a good question! Hope someone can answer that as I would like to know too!
you have got to let it dry for a few hours. you could try the glaze but it may change the color or cause the gold to run. practice before using on real cake.
usually I try not to touch the cake, but you can always go back over the area again when you are totally done with the cake and touch up any white places.