The methods that would work in a photo (The Healing Brush, for instance) won't work well in video because you'd have to follow the face wherever it appears in your video frame.
They sometimes do this kind of thing in Hollywood. (Hiding someone's tattoo, for instance.) But it's a frame-by-frame touch-up and can a cost sometimes hundreds of thousands of dollars. And I assume that's probably not in your budget.
I would use Track Matte Keying on the person's face, and do a slight Blur, to smooth out the skin.
There used to be a great tutorial, on doing just that, but Curt Wrigley closed down his Web site, where his tutorial was hosted - very sad day.
I did a written tutorial, on using Track Matte Keying to "Highlight a Moving Subject," and with a bit of interpolation, you can use that. All of the general steps are in it, but in that tutorial, I used a hard-edged "circle" to do the highlight. In the case of a person, you would use a Track Matte with soft edges, sized to about the person's face. Here is that written tutorial: http://forums.adobe.com/message/1765005
Good luck, and hope that helps - too bad that Curt's tutorial is no more. I would have hosted all of those, had he only asked.
Following someone's face with a Track Matte and making it look natural would be all but impossible, Bill -- unless you mean to blur the face like they do on COPS.
Seriously, the only way to do this and make it look natural would be to output each frame of the video as a separate photo and then touch up each frame individually. (There are 30 frames for every second of video.)
Well, much will depend on how much the face changes in Scale, shape and Position, but if only part of it needs a little touchup, it does take some hand-work, but is not that difficult.
In Curt's old tutorial, the "bride" was doing an interview, but was moving a bit. The "softening" was done on most of the face, with the eyes, and mouth not affected.
Had she been running in a field, and turning her head, from side-to-side, things would have been a lot more difficult, but then, it would likely have been a much wider shot, and blemishes would not show clearly.
Just wish that Curt had not trashcanned everything on his old site - there was so much useful material there, but it is gone forever.