Screening, Motivation, and Equipment
MEM:
Nicely said.
Another variable in the civilian world: students can be a varied group. Old, young, educated, and not so much, top performers, bottom-scrapers, lots of free time (frequent lessons), working adults, lots of spare money, and just getting by (infrequent lessons).
The military student fits into a 23-28 year group most of the time, some are as old as 30. In the USAF, all have a 4-year college degree. They will fly 3-5 times a week on average, and do nothing but study flying for a year.
You don't get that kind of screening, nor ability to intensify training (usually) in the civilian world.
However, the fundamentals of how airplanes are flown remains the same. Granted, a C-152 takes a different feel than a Block 50 F-16, but the basics are the same.
The biggest hardware difference I see: the general low power-to-weight ratios of light GA aircraft, the limited and haphazard IFR instrumentation, and limited understanding of P-Factor in most military pilots (T-34, T-6, C-130 and E-2/C-2 pilots being notable exceptions!).
I think the transition will be easiest for those who have some prior experience in the GA world. Failing that, though, I would hope any aspiring "Instant CFI" would do what all of us did as military IPs:
Gain credibility through experience. I wasn't able to instruct in the T-38 with 5 hours in the airplane; I had to complete PIT; nearly 100 hours in the jet. When done, I still didn't know a lot about teaching in it...I flew as much as I could, without students, to gain experience.
And if I ever teach using the CFI rating, I'll do the same thing, in whatever airplane I'm going to teach in.