CFI training
Of course, every school offers the best training possible. And, of course, every school claims it is the only way to the airlines. The answer to your question is, well, a lot depends. You want to be careful not to be penny-wise and pound-foolish, because you'll end up paying (through the nose) in the long run.
I did all my studying at home. I don't feel that I learned it as well had I gone to class, studied, prepared assignments, taken notes and interacted with the instructor and class. I saw the difference. I went to class for instrument and CFI-I (weekend class) and ATP and FEX (weekend class). I got a great deal out of those learning situations.
The airplane time you need may well depend on (1) how well you are now flying the airwork and (2) how quickly you can learn to fly out of the right seat. Most of the flying is the same, but landings are strange at first out of the right seat. Bottom line about the flying is each CFI is a single-engine airplane, instrument rating, and multi rating ride(s) out of the right seat. If you can pick up flying from the right seat quickly and fly it all to standards, you may well have the same experience as Ned. Most CFI students I had needed the full 10 or 15 hours of course time to hone their maneuvers from the right seat.
It is more than important for you to have all three airplane ratings, so you are completely qualified to instruct everything. I do like the idea of earning Commercial and Instrument in the multi and then jumping into the right seat of the multi to earn intial CFI as an MEI and CFII. You can really maximize the value of your (expensive) multi time that way. Morever, the information will be fresh in your mind. You can always pick up airplane CFI later and do it in a fixed-gear.
Finally, it may well be luck of the draw if you get FSDO to give you your practical. Depending on the FSDO, it could well send you to a DE and you'll have to pay. Opinion seems to be split as to whether a DE gives an easier or better ride versus FSDO.
Hope these thoughts help. Good luck with your plans.