Use Gum Arabic to make glazes... mixing it with varying amounts of water. It can used as a glaze for marzipan, or an edible glue for gumpaste. Used as a glaze it gives the decoration a glossy sheen.

Instead of airbrushing, try handpainting with paste colors. Thin paste color with consumable (grain) alcohol. Alcohol, rather than water, is used for thinning because it evaporates quickly upon application. Paint directly onto the icing's surface using a soft bristle brush. Stencils may be used when painting, too. Have fun!