Here are some updated tips for modifying brushes. The biggest change from my original brushes is the process. You will need to have looked at, Simple Brush Modification With Model Magic to understand the rest of this post.
When I make the model magic handles, I no longer poke the brush handle into the wet clay. I found that it’s better to wait for the model magic to fully dry and to add the brush will later. Carving out a whole after the play is dry creates a tighter fit for the brush. Once I lock in the brush with glue it is much more stable than the previous set I made. My favorite glue right now is a clear outdoor sealant. It seems to bond well with the model magic.
When the wooden brushes get sawed in half, it often loosens the brush had. To prevent this from being a problem I’ve been adding duct tape as reinforcement.