I have to do a cake in the shape of a crab but I don't have an airbrush machine to make it look like a real one. Is there a way to color it by hand without using an airbrush machine?
You can try painting it on with food color mixed with clear alcohol or vanilla or lemon extracts.
Experiment with the colors until you get the effect you are looking for like paint it in different shades of the same color to get a more realistic look.
try sponging for a more natural look. layer on the color for a richer color. good luck
Try a mouth atomizer (poor man's airbrush)! The run anywhere from 2 dollars to 10.