I found my method of using blu tak (re-useable adhesive putty) to be great for me as I could use it to add extra weight. I could put in too much and then remove what I didn't need and it is readily avaliable.

But I love the idea of using a brush that includes some intersting coins. Imagine using semi collectable Chinese good luck coins or foriegn coins from a favorite holiday destination. I'm sure it wouldn't inprove that value of the brush, but it would give it a little more sentimental value.