Use a wipe with a very feathered edge between sharp and blurred footage.
Or duplicate your footage, and blur the copy. Then use a B&W grad matte to control how/where the blurred footage composites thru the sharp footage.
Scott Sheriff
Director
http://www.sstdigitalmedia.com
"If you think it's expensive to hire a professional to do the job, wait until you hire an amateur." ---Red Adair
Where were you on 6/21?