I wish I could remember which blogger recommended the BrushEgg. I found mine at aliexpress.com and it just arrived yesterday.
I would describe the BrushEgg as a mini washboard for makeup brushes. It is made out of silicone and seems pretty durable. You put a dab of your cleaner on the textured side of the BrushEgg and gently rub your brushes back and forth to clean. Smaller brushes can be rubbed against the little nubs and bigger brushes can be rubbed against the ridges.
I’ve cleaned one brush with it, and so far I like it.
BrushEgg @ aliexpress.com (took 16 days to be delivered – pretty quickly for a package from China!)