I realized in February that the email blast to strangers was not going to work. I have emailed about 100 teachers: two have replied with no commitment, and a third says he is interested after finals.
However, approaching friends (and friends of friends) is working nicely. I have dates in the calendar for a math teacher and a chemistry teacher. I have a four English and two Math teachers who would like to contribute when they have more time.
I suspect that summer and vacations will be very busty times for me since that is when teachers can film most easily. The rest of the year will be spent on the site and on marketing.