This project can still be done with new brushes you can easily find at the Dollar Store. I get my budget brushes through Nasco, and with their 20% off code, it's less than the Dollar Store.
I have students choose a brush and trace it onto sketch paper. Then we talk about all the possibilities. Having some sketches on hand may be helpful based on your own personality as the teacher.
1. You as a future artist, paint splotches and all.
2. A paintbrush muse to inspire your creative spirit.
3. Create a paintbrush portrait of a famous artist.
4. A monster to blame for when your art doesn't go as planned.
Each lends itself to additional connections. Careers in art, Greek & Roman mythology, art history connections, or just silliness, respectively.
The nice thing about this little project is that there are many different media you can use for the 3D effect: Sculpt-it, Model Magic, Salt Dough, Air-Dry Clays, Paper Mache Pulp, Plaster, Acrylic Modeling Paste, etc. (We even used Wonder Bread kneaded with white glue as a base!) Each student had about enough to fill a 4 oz paint cup and it turned out to often be too much. So this exploration will use up all your material.
Paint it up with whatever you have as well. Add little bobbles and trinkets if you have any handy. When appropriate, some even gave their brush a bit of a haircut!
This was a lot of fun, and I may incorporate more recycling in the next go-round.