The CFI initial.
Wikipedia has some great stuff for FOI
For the aviation specific stuff, I'd tutor some folks for free.
Airwork is nothing, you should already be there, might need a endorsement for spins, but I'd have imagined most CPLs have some spin time already.
The initial CFI was the hardest ride I've been on (FSDO ride), it was also the least amount of money I've paid for any ride, it's all self study for the most part.