Write these down. It is not useful to draw interaction diagrams for all the scenarios considered, but it is very useful to draw a representative few. This is very effective, since it allows quiet, thinking time to mix with sharing and evaluation. The typical resistance modelers feel to CRC cards is that it involves designing in groups and out loud. This resistance is what causes CRC not to be practiced as much as it might.
Modelers are more comfortable staring quietly at instance and object type diagrams.