New Sandpaper Brush - Budget Tip

I bought a new sandpaper brush today.
I use the brush to knock off accumulated primer sanding dust from 400 grit sandpaper.
400 grit loads up quickly, especially when you are dry sanding the first primer coat.
You can remove the dust "mud" by brushing the sandpaper under running water. You shouldn't have to brush very hard to take off most of the loaded up primer.

This brass brush is like the old suede brushes. Over time the rough sandpaper will wear down the bristles. My previous brush lasted five years.
This new brush is the WorkForce #330761, $3.19 at Home Depot.
The amount of money I save by re-using sandpaper will pay for the brush many times over.