Training Java devs on COBOL - what actually worked?

Management approved a two month rotation for Java devs to learn COBOL basics. Half are curious, half think their career is ending.

If you ran something like this, what kept people engaged?

Pair on a real small change. Fix a report field or add a validation. Slides lost them.

I came from Java. Copybooks as DTOs plus one week of JCL context made batch click.

Update: one week batch, one week online. Way better feedback than the PowerPoint week.