Thanks for all the advice. I use a lot of those sources, especially lately with all the new stuff.
Sometimes I run into the classic "using the thing to define the thing", which can be a little frustrating, and will start making a list when I run into it again. And more simple examples in places would also help. Sometimes examples are there and sometimes they're not and I will make notes and send. Generally I can find what I'm looking for through Help or online sources. Sometimes not.
All the best,
m

I always seem to run into ambiguous, non-helpful entries in the "Help". Should I send these to the "Suggestions" or is there somewhere else to send them?

Ha ha. IDK where "screen-paint" came from. Changed my screen name.

I just figured it out.
In the Particle Group Cache tab uncheck "Use Animation".
Then, animate the "Frame" parameter.
I pre-rolled my 300-frame particle sim starting at -60. So my sim is 360 frames long. Once I had the Cache built, I set a keyframe for Frame at 0 and the another Frame keyframe at 300. It defaults to linear, so I just needed to set the "After" property of the keyframes to "Repeat".

The "Help" file kinda says this but it's ambiguous as usual and took some experimenting, but glad I figured it out.

So that works, but how do I use the cache file without the "preroll" frames (the frames before zero)?
I would like to loop the full particle build without the starting frames.