In my opinion to develop a new modder into a good one instead of a bad one (shame we don't have a Darth Vader smiley) the best way is assigning him a personal tutor.
The best way would be to communicate via chat and/or PMs in an environment where the pupil can ask the tutor anything they like. The tutor should, whenever possible, give quick answers, and if need be, explain it to the unexperienced in easy words
This of course means a major time commitment for the tutor, so this can only happen inside a mod team and if the elder and potential pupil like each other (because you are more likely to spend time doing stuff for people you are fond of).

In a community-wide point of view, the best way is probably to have as many experienced people around as possible who answer questions (when I was more active I usually tried to check the questions forums at least once every day here and on the TWC), and by having as many tutorials as possible.
What do you think about creating a tutorial request thread for M2TW where, if you discover one of the gaps you mention, you can request that a tutorial is written about it, or it is fitted into another tutorial. If anybody has the time to do that then, they have a number of topics they can write about.
This, of course, requires a number of experienced modders who are interested in sharing their knowledge and have or take the time to do so (I know that this is not easy from personal experience), but as there aren't that many people around who write tutorials at all, I guess you can still find a number of persons who would do that (and if it is only to avoid being asked the same questions over and over again).