You can try a variety of blurs to see what works best. You can also usually get a slightly better image by laying a new copy of the bad vid on top of itself, process with blurs, noise reduction, and unsharp masking, then reducing the overall opacity of the processed version to blend with the unprocessed or lesser processed version.
They are designed for exactly your problem. Do a few samples and test on your monitor before you do the whole project. A little smoothing goes a long way.