I made a brush that writes my first name, in my own handwriting, in cursive. https://i.imgur.com/gGDbSJt.gif
There are not many opportunities where I can share this and people will understand what I'm talking about. I just felt like bragging. Carry on.
You might be better off using steel ball bearings if they aren't going to be visible. From a casual search it looks like steel is cheaper than glass as far as balls are concerned.