[Getagb]

I figured out the first part, and decided to post it for anyone wondering:

To make the white background of the video transparent, apply the Image Mask filter (Video Filters -> Matte -> Image Mask).

The explosion looks great except that it’s black. Any tips on making it look like a ball of flame? Worst case scenario, I can de-saturate everything so this scene’s in black and white, but I’d rather not do that.