"Critical thinking" isn't what I am talking about. It is about showing linear thinkers how to be able to take the solutions and processes they know and to be able to associate that with what might seem to them to be things that are totally unrelated -- how to free associate, determine what applies, and to draw relationships. For those on the other end of the spectrum it is about how to limit the association and be able to draw lines to things that directly relate to the problem so that concrete relationships can be formed and a solution can be arrived at. In this way, a solid two dimensional thought pattern can be attained.
Next, it is about how to concurrently solve multiple problems along multiple paths of related constructs and to explore the limits of what they can associate in order to gain a three dimensional thought process. Not everyone will be capable of doing that. Some will go further to fourth dimensional thought and genius can blossom.
By necessity, this is done with an individual focus, though it can be accomplished in a group as long as your level of management can support it. The time it takes is offset by the reduction in time that the "subject" matter can be processed. In the end, instead of merely remembering what you have taught them, they can truly understand it.