I would suggest two other skills.
Firstly social skills, and whilst I'm not the biggest fan of CRM because is is impossible to run a 2 man crew on one man one vote principles, if two people are working together whether relining a wing fuel tank with a rubber liner, or doing a let down into an airport with terrain problems then communication is vital.
The second one which I think is even more important is logic/problem analysis/common sense call it what you will. You can be able to qoute every manual to the finest detail, but when it all turns pear-shaped then there is no substitute for quick thinking and common sense. How you teach or acquire those skills though is a different question.