How to stop lead dust from escaping shroud back-vent holes?

The shroud on my wildcat is drilled towards the rear to back-vent it. I am wondering how I can keep the back-venting but also contain the lead dust inside the shroud which I can clean periodically? As I have it now it splatters lead dust on the underside of my scope rail because the holes are aimed straight up. Any suggestions on how to keep the LD in? I don't want to turn the shroud sideways so it just blows out the side of the gun either. If I can't stop it I'll just get a new shroud.
 
I took a ride the the dollar store yesterday and picked up some plastic hair curlers and a scotch-brite pad. Wrapped the outside of a curler with one layer of scotch-brite and it fit perfectly inside the shroud. Now my shroud still vents but I don't get hit or feel any of the air when firing (which just made me uncomfortable for some reason). It does seem to be filtering the LD okay but I haven't used it enough yet to be sure. I can always try different materials in the future.