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During the workshop simply let people follow the https://github.com/apache/airflow/blob/master/CONTRIBUTING.rst#contribution-workflow-example . Make sure to update template and remove replace sponsor's material with the actual sponsor.
Before people leave, you can give people the survey you can print and ask your attendees to fill. With 20-30 participants it is best to give printed survey to fill (people will fill it) rather than send them electronic survey. Link to Google doc here and .pdf version is attached. Make sure to share results of the survey with your attendees.
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