I didn't do it this way, but I would be interested to think what other people think of the following:
1. Study for your Commercial and CFI Oral at the same time. Attain instructional knowledge in all the CSEL areas.
2. Take your Commercial Written, CFI Writtens and AGI written all at the same time.
3. Prepare for the CSEL flying portion from the right seat and attain instructional knowledge/demonstration in all of the Commercial Maneuvers. Talk your way through all of the maneuvers from the start.
4. Take the CSEL Checkride from the right seat (a cfi-friend of mine did this), schedule your CFI ride the same day you pass the CSEL.
4. Prepare instructional knowledge of PSEL and CFI parts of the Oral (endorsements, etc.)
5. Practice the private-only flight maneuvers from from the right seat.
6. Take the CFI Checkride.
This assumes, you have a complex single available, have the money to pay for your CFI and Commercial at the same time and have completed all of the necessary written exams.
The CFI check is the hardest, in part because there is just so much you need to know. I took my CFI checkride about 15 years after my private and 5 years after my commercial. I wish I had done the commercial and the CFI much closer together. But then again, I never thought I'd want to get my CFI rating.