Slow shutter effect in videos

Hey family, I am just working on some footage and am wondering "how to create a smear/ slow shutter effect" in post-production?

Maybe you can help me?

I mean, there are camcorders who have the slow shutter effect inbuilt (recording at a shutter speed of < 1/30s) but what if the shutter speed was normal? not using AE

Undersampling is not working ( < 25fps) and I'm not talking about a slo-mo effect, but would like to generate the fire trails, like on this vid (shot with slow shutter) in post production, NOT using AE



thanks for taking the time

Oh yes - I'm working with Vegas Movie Studio and there is no "posterize time"....