If you want to pick random records, you will need some sort of scripting.
One way is to go with a completely customized script that picks random random records, marks them as picked, and resets records when they are all picked. If you are familiar with scripting this would have fewer actions and could put all the logic in one place.
A method that doesn’t require any JavaScript skills would be to use the Batch Update extension to fill all records with a random number. Create a view that is sorted on that random number and filtered to only show unsent records. Then do a “Find Records” action that picks up the records in that view, and use my Automations Helpers script that tells you the first records from a “Find Records” action. (The description says it gets you the first record, but it actually gives you the first three.) You may use the script multiple times: once for each field that you want to include, and again for the record IDs so that you can update them to a sent status. (You would need three update record actions, one per record.)
