I just created a simple object with custom brush as a stroke.
Is there a way to divide that stroke in a way that I can choose where the new brush ends and another starts - still surrounding the complete object?
I answer your question as I'd do solve the task, other users will give you their ways.
The simplest way IMHO is EXPAND the path, and cut it using KNIFE tool and apply the brush to the objects created:
Let's say we have this path -
I EXPAND (Object-Expand) it, then I cut it with the knife tool in 2 points
and automatically get Group of 2 sub-objects.
Next, I choose every object in its turn and apply the Brush to it: