The local maxima i am aware of here are:
1. Outdated books. When i learned Perl i wasted a lot of time on books that are now known widely to be objectively bad, but are still recommended widely. The ones i recommended allowed learning with little friction.
2. Algorithmic and semantic problems that have to be resolved through lengthy investigation sessions long after they're implemented. I spent a LOT of time figuring out what doesn't work well in the long run. He's been able to skip those and spend his time more productively on problems that i haven't encoutered or solved yet.
I'm not trying to toot my horn here and i think i'm not a good teacher. But the advantages he had from me being available were staggering.
(The wordy rant to offset my quotable. ;) )