Today, I taught the National YOG squad how to paddle hand roll in about 30 mins *grins*
I've found as a rough guideline that the following is true.
1. You can teach athletic people (helps if they have a solid kayaking foundation and solid core strength) to paddle hand roll in 30 mins to an hour- close to 100 percent success rate
2. You can teach athletic people (same as above) to Eskimo roll in 4 hours- close to 100 percent success rate
I reckon you could teach quick learners in a one to one session under 2 hours. And it really does seem that it you teach them the basics right, they get it 100 percent.
3. You can also re-teach people their roll if they have a non-100 percent one- most likely their foundation is not strong or they might have the wrong concepts even. Have guided a few coaches to re-learn their roll and the results have been very pleasing. (I think Jessica's roll is even prettier than mine sometimes, dammit *grins* but mine is still more powerful *grrr* -goes away to practice a prettier one so that I won't paiseh)
Apparently, the creator of the C to C roll could teach people in about an hour- He betted that against a free lunch or dinner, and word has it that he was kept well-fed for a long, long while! I'll get there if I can!