Don't use blending modes for this.
Use channel mixer or a similar effect to make your red smoke layer pure white. (Unless you made it look red for this use and it was originally white, in which case, just use the unaffected version of the layer.)
Use that as a
track matte for the footage you want to reveal. Apply Levels as necessary to make the people more opaque.
And put a copy of your red smoke layer below it all.
- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')
No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.