Muzzle flash and environmental glow

Hi

This is a tutorial by Freddie Wong on how to make realistic muzzle flashes.
http://www.youtube.com/watch?v=SsViAvVYoMQ
I'm trying to do this in Kdenlive but I can't do the "environmental glow" he's talking about starting at 1:48.
I copy the clip and add it to the underlying video track and apply the "addition" transition.
But that transition applis to the whole screen. I cant mask it like Freddie does.

Any ideas?

Would the rotoscope effect be helpful?

Thanks for the reply.

I've tried the rotoscope effect but it doesn't seem to work with the "addition" transition.

You can do it using Rotoscope.

Check this screen shot I just made in a test project http://userbase.kde.org/File:Rotoscope_for_enviroment.png

Video track 2 is a copy of the file in track 1 but with levels adjusted to make it brighter.
Composite transition between the tracks.
Rotoscope effect on track 1.

Thanks! I'll try out later this weekend.