Focus on specifics

Following up on the idea of focusing on strengths, one can also try to focus on specifics.

Rather than try to engage a whole school of thought--pick a specific writer/thinker in that field.
By doing so, you reduce the amount that you have to research and you create a more focused discussion.
A whole school of thought will be characterized by a wider range of ideas than a single author.

Or try to focus on a specific premise instead of a whole school. Rather than focusing, for example, on Marxism, focus on the class dialectic; instead of focusing on Post-Structuralism, focus on the premise that Truth structures are related to political power.

And these are not cheap shortcuts--they are ways to focus and strengthen an argument--rather than dealing with broad strokes and generalizations, you focus on the important specifics that are the central issues.