I've tried to find a video on how to make a brush dynamic like scatter, different rotations, sizes, etc........but I can't find one.

I've downloaded a few pearl images brushes, and can only seem to place them on the page exactly the way they were originally, even though I applied jitter to the brush. There just doesn't seem like there's a lot of options unless I'm not seeing them? Even if I want to change the angle of them, I would have to do that manually to every pearl I put down? I have Gimp 2.8.16

I do not think you will get the effect you want easily. The settings you should look at are brush dynamics.

https://docs.gimp.org/en/gimp-tool-dynamics.html plus plenty youtube videos if you search.

One thing to note is brush spacing. This is a percentage of brush size, not a spacing in pixels.

The default pre-made dynamics are write-protected, so you need to make a copy of one (say, dynamics off which is blank) which you can then edit.

some examples:

No dynamics - regular brush - https://i.imgur.com/oNgFUYM.jpg

Size varies with velocity https://i.imgur.com/SsCJ54u.jpg

More than one variable - size and spacing https://i.imgur.com/G5f36J2.jpg

Random size https://i.imgur.com/pY21zSD.jpg

Size and angle https://i.imgur.com/DBh0Yk5.jpg

rich: www.gimp-forum.net

Where do I find that mapping matrix?

Shown in the Gimp docs if you look. The correct way, Windows -> Dockable Dialogues -> Paint Dynamics to bring up the list of dynamics. Then use the edit icon to bring up the Mapping matrix. see screenshot1.

As with most Gimp there is another way. The dynamics icons in the Paint tool options do the same as above. See screenshot2

Looks like you could do with an easy way to browse the Gimp help pages. You can get a PDF version here: http://gimp.linux.it/www/meta/ It has a good searchable index.

rich: www.gimp-forum.net

Ok thank you - I didn't know to look for brush "dynamics" videos in google - I was looking for a few terms that brought nothing up, lol!