CFI schools
A lot depends on how much you want to spend and the type of training you want to receive.
Any of the major commercial flight schools, such as FlightSafety in Vero Beach or Pan Am, offer CFI courses. I don't know if you can go to Comair just to get a CFI. I know FlightSafety's course because I taught it once upon a time. It is thorough, and expensive. But, you do get very comprehensive training. As always, much depends on your instructor.
Sheble Aviation in Las Vegas,
http://shebleaviation.com/ , offers a quick course for less money. I went to Sheble for my ATP years ago. Very informal. The course is accelerated and I don't know how thorough it is, but I haven't read any complaints.
Finally, Airman Flight School in Norman, Oklahoma,
http://www.airmanflightschool.com , is supposed to have a pretty good and fast program. Moreover, you can't beat the barbecue in Ada, Oklahoma, just .8 away!
Hope these ideas help. Good luck with your training.