I've read a lot of forum posts with people asking how to do this but never found a simple solution. Here's how I made it work for me.
Press F11 to open Styles and Formatting
Click the second icon Character Styles
Click the word Bullets
Right click Bullets and select Modify
Select the font Segoe UI
Change the size to 14
You will see that style automatically applied to all existing bullets in the document
The point of doing it this way provides two solutions
The end user will always get the correct bullet size. If they indent a bullet then the next level of bullet will also be that size. When defined in your templates, all the user needs to do is click the bullets button and it works.
By setting the font size to 14, this provides additional spacing between the bullet points. Once again, when defined in your templates, all the user needs to do is click the bullets button and it works. This is of course relative to the font size you use for your paragraphs etc.
If you are wondering why I chose "Segoe UI" as the fonts for bullets, do the following
Right click a bullet and select Bullets/Numbering
Click the Options tab
Click the Character "..." button
Here you can see that this is the font being used by the bullets
Another alternative is to change the character being used by each bullet level. This seemed a bit more involved and wasn't something I was interested in getting into.
Hopefully these steps will provide help for people who don't know where to find some of the default options.