I know I'm rating it a little high for just an OVA/Special, but I really enjoyed it. It an odd coincidence that I found this right in the middle of season three, but its extremely pertinent to watch this before the licencing exam arc in season 3. Otherwise, it looks like they had no rescue training at all. Especially Yaomomo's explanation of what to do and not do during a rescue mission had clear connections to Deku's reaction in episode 18 and 19 of season season III. ALSO THE STAIRS IDEA USING STUPID MINETA'S BALLS WAS BRILLIANT. I hate how useful he is lol.
tldr; Make sure to watch this before season III