Adding flying debris

So now we are going to create all the debris that's flying from this explosion way off in a distance.…Now it sounds complicated, but it's not, it's just creating a brush.…So what I'm going to do is I'm going to take my Marquee tool here, and I make sure I'm…in a layer that's mostly transparent, and the front smoke is mostly transparent.…So I'm going to go up right here. I know there's nothing there. Let's go look at that layer.…See? There's nothing there.…So I'm going to just create long little rectangle like that.…And I'm going to go ahead and fill that with black.…

I have it selected still, so I'm going to say Define Brush Preset, and we'll call it debris.…I can throw it away, you select it, it's gone, but it is a brush.…So I'm going to go into my brush and select-- there it is right there. It's just this little…black which you know it's going to do this. It's got some modifications now, it's got…a full opacity, and you could see it's just doing that. It's following whatever I set…up for the smoke the last time.…