I just found the Color Finesse plugin for After Effects. This makes is really easy to make a very quick and, to my eyes, pretty accurate white balance correction -- just using the gray eyedropper.

For much of the video I do (classroom stuff) it would be easy enough to make a little gray card to put on the surface in front of the teacher to film while taking a sample of the audio room sound (I do this when I can for most classes). Question is, how gray is gray? What level of gray does Color Finesse expect for that function? IOW, could I use something like a Kodak 18% gray card? Nice and neutral with no metamerism. So they say.

Alternately, does this make any sense? Or should I just do a manual white balance in the camera using said gray card? Would it matter? Would there be any difference?

I know, try it and see. And I will do just that. If I can figure out what gray to use to white balance with. I can't be the first person to ask this question, but Google hasn't been my friend today. Anyone point me in the right direction?

Yes, you need a chip chart that contains black, white and 18% gray. You can white balance your camera using that card. You can also use it in color correction within Adobe Premiere Pro or After Effects. Here's a link for a chip chart: http://www.kozco.com/calibrat/gray3.html

More on using the chip chart in post: Color Correction for Digital Video ... - Google Books (http://books.google.com/books?id=s3rQjdG2pBUC&pg=PA48&lpg=PA48&dq=chip+chart+for+color+correction&source=bl&ots=XS3V8Sx0BN&sig=8lWv8ICc3WYgvf9qfOjAX621SEk&hl=en&ei=HksvTajhPM6GhQeWydjmCg&sa=X&oi=book_result&ct=result&resnum=6&ved=0CEMQ6AEwBQ#v=onepage&q=chip%20chart%20for%20color%20correction&f=false)