Sort the cards by category. Divide a sheet of paper into 4 quadrants and label them (A) Invoked exceptionally well, (B) Invoked competently, (C) Could have been invoked, or invoked more effectively, (D) Not applicable. While observing a facilitator, move cards from the sorted stacks to areas A, B and C of the paper, attaching post-it notes with brief annotations and explanations to the cards as you do so. If observing an expert facilitator, focus on the cards you're moving to area A, and reflect on what you can learn from their example. If observing a student facilitator, focus on the cards you're moving to area C, and what the student can learn from your observations. Note any clusters of cards from a single category that are in areas A or C. Consider taking a photograph of the completed array.
This same exercise could be used to ask your co-facilitator or another participant in an event to assess your facilitation of the event.