Yeah, I've played with it just slightly, but have trouble figuring out correct prompts.
Discussion
If you have a very defined and repeatable prompt that you just want variations on, I find a custom bot works best as it keeps all the data associated with those generations in one place.
But the trick for me for general stuff is just to spell out what I'm looking for with a lot of detail. There's a lot of "Try again, but..." followup prompts. 😂