If you're trying to do what I think you are, the term is film burn, and how I like to see it done, personally, is to have it begin in the first clip, escalate to 100% opacity and dwindle it down into the next one so it's more a of a transition. You can download templates for free online if you search "Film burn download" or something.
If NS had an anus this thread would be pounding it. -sndyrvr
Hello future me,
I had no expectations for you. So anything you have done is a plus for both of us. Good job! -iAfterBang
Yeah film burn not a lense flare. What you need to do is find creative ways to use it. It's obviously be around forever well as long as film. Because of that most people have seen it so coming up with a cool way to use it is key. Try confining it with other techniques like roto or other effects so your not just adding it over a piece of video