Basic multiple luma-keys

Foreground was a frame of white

flame

Make it Snow
Clean Plate
Action> Particles > Lens blur :-)

One on many luma-keys. Erode was handy here.

Final Comp including Tinder sky and some placed low cloud.

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multiple particle passes for depth and speed

Same kind of treatment . But had to roto the guy.

Painted a Z-pic and used Sapphire ZFOG.