What I've had the most success with is an image I found online for an actual muzzle flash.
Here are some good examples:
http://images.google.com/images?svn...e+flash&spell=1
Basic cut and paste on those flashes, adding some blur, that might work for you. Not sure how Corel works compared to Photoshop (which is what I use) but those might offer some info, anyway.
Justin