This question has two parts.
Pedagogically, what is the relationship between kata and bunkai? I comprehend why the solo kata form is useful and important and why the investigation of bunkai is crucial. I'm not asking for people to justify their attitudes towards those practices. In your various dojos, when do you teach kata and when do you teach bunkai? Are the solo forms taught side by side with their corresponding bunkai? Is the solo form taught first with a large time gap between then and when the bunkai is introduced? Is the bunkai taught first, with the solo form taught as some sort of souvenir only after students master the techniques? Does a student learn a kata and its corresponding bunkai as part of a single grading or do you split it up?
Secondly, what is the relationship between primary and secondary bunkai? Primary bunkai generally refers to the applications that are taught first or considered the most readily applicable or the instructor's favorites. Secondary bunkai refers all of those other valid applications that do not serve the role of primary. When do you teach secondary interpretations of kata movements? Do you teach them at all? Do you allow students to create their own interpretations of kata? How do you go about conducting such an exercise?
I look forward to hearing what everyone has to say on the matter. :)