My advice is: Don't bother. "Dot filtering" is simply another formulaic fad, similar to the overdone "pre-shading," "post-shading," and the latest, "color modulation," which have given us nothing but cartoons and caricatures of real objects rather than scale models.
More advice: Don't follow someone else's "cookbook" approach to painting your models. They will all turn out looking like their models, rather than the real objects they are supposed to portray. Real objects, whether they be tanks, ships, cars, or aircraft, do not weather in accordance with a formula. Rather, study photos of the real thing and develop your own techniques to acheive a realistic look. Also remember that subtlety and understatement is the key to achieving an accurate weathered look. If you think your model needs more weathering, stop; it's already weathered enough.
Michael McMurtrey
IPMS-USA #1746
Carrollton, TX