For me, I prefer using them on hard soaps, like pre de provence 63. I find my synths, to be great on soft soaps and creams. However, I have an Omega Boar, would love to try a SOC.SOC w/ Omega soap.
Does anyone else feel that boar brushes work best with soft soaps? I always get better results with them than hard soaps, but alas I rarely use my SOS so its most likely at least partially technique.