How do i use matte in AE?

[Burlesque]

When i'm making explosions on film i often use explosions from Artbeats Stock Footage. With every explosion in the volumes i bought there are also a matte version of that clip.

I now want to learn how to use the matte versions combined with the real explosions to create a better realism.

How do i use the matte clips?

 

[milksac]

Put the b+w clip on a track above the color clip. Set the track matte for the color clip to the layer above (b+w clip). Read the help files about track mattes for a more thorough explanation of the process.

Another technique to key out explosions shot on a black background is to use Knoll's unmult effect. You can download it for free at Red Giant.