I too am a little confused about what exactly you're going for, but I think I have an idea.
In regards to the dust .... you're right, cotton balls just look like dirty cotton balls. I went through something similar a little while back and while I can't remember the exact wording of the advice (but I know Hans gave it) ...
It basically boils down to this .... Modeling, specifically dios, are a snap-shot of time. They represent action, not show it. Dust, smoke, etc, while able to be captured in a photograph, it's very difficult to model it ... and it looks like poop. So what to do ... the best thing we as modelers can do is model the aftermath.
In short, I think the best thing for you to do is to have the "head" already crashed w/ the figs, I'm assuming are riding in the head, already bailed out, rendering aid to injuried and just overall trying to get a handle on the situation. The "hand" providing cover can be hovering there, however, consider the time it takes for "the cavalry" to get to the scene. This will help determine what your figs are doing.
I hope this makes at least a little sense.
With all that said .... I'm getting ready to build a helo in flight ... w/ whirling blades ....
... guess my advice/ opinion just shot itself in the foot!?!?!