do I free hand the camo design or as suggested by my local model shop mask with white tak?
For my three planes I first airbrushed the whole top of the model with one of the camo colours, then used white tack, rolled into worms about 3 to 5 mm in diameter (depending on scale). I put pieces of
Tamiya roughly shaped tape (yellow) over the parts to be protected from the other colour. Then I sprayed, holding the AB at right angles to the surface. This gives a fuzzy border.
Note that the second colour covers more area than you think because of the spray that gets under the white tack (which it has to do to give the fuzzy edge). Therefore you might want to expand the areas which protect the under colour to compensate for that. Note that White Tack and
Tamiya tape stick to each other very firmly and it is very difficult to separate them, so I just discard them.
If you are content to have a sharp border, simply stick on
Tamiya Tape cut accurately to the shape.