I did a very decent muzzle flash effect a while back. I found that if you, as suggested here, you take the single frame into a image editor (Photoshop/Paintshop Pro) and find a JPG/GIF etc. of a flash:

http://www.matthawkins.co.uk/special...e_flash_sm.gif

...Or whatever, and lay it over the end of the gun, sizing it as appropriate. Then, to light up the area around it, use a large air brush with 10-20% opacity, to give the frame a little more life. Then bring it back into the video.

If you spend a little time, you get quite a nice effect, and though it can be a little annoying adding it to each gun shot in your production, you soon get quick at it.

Also, try adding a little smoke, like so:

http://forums.creativecow.net/cgi-bi...oke/index.html

Hope I explained well (Im under the influence of alcohol....)