Airframes
Benevolens Magister
That's the basic idea Glenn, but also, start to 'only just' let the paint flow. If your Sotar has the adjuster on the end, to stop down to the desired setting, the set it at minimum opening (fine line). You should find that paint will not actually touch the surface before you line-up, when the trigger can be progressively opened further. Being on 'fine', it's then possible to build-up each mottle as required. At worst, there may be a very, very light over spray, which then acts a a diffuser, softening the overall effect, without detracting from the finish. This over-spray is so fine, it can only just be seen if it has overlapped a masked area, with a light background, once the masking is removed.