Serious creators already have a system for creating videos for their digital content. So creating on the fly using YouTube shorts is really not a viable option for them. The best way for the pros to get their videos on the Shorts portion of YouTube only requires a few things.
Your Video(s) must be 60 seconds or less in duration.
They need to have this hashtag in the title or description #Shorts
You will need to upload them in the vertical orientation like 9:16 Aspect Ratio
After that you simply use the upload method you are already used to on YouTube and they will recognize the video and place it in the Shorts section on the platform and on your channel.