Eric - regarding camou application on Italian armour, I haven't ever come across literature stating exactly the methods of application. From photos, particularly those taken in museums, they do look airbrushed.
I've no idea what pattern you plan on doing, but seems minute and intricate? If so, hand brushing it is a valid option. Followed with a light re-spray of the base colour to reduce the harshness should be fine, or if you use any of the filtering, glazing techniques that too should do it.
regards,
Jack