Synthetic Kabuki When It Comes To Kabuki Brushes For Smooth Buffing Of Minerals, Are NATURAL Bristles Better, Or SYNTHETIC?

When it comes to Kabuki brushes for smooth buffing of minerals, are NATURAL bristles better, or SYNTHETIC? - synthetic kabuki

Furthermore, the type of animal hair (goat, horse, sword, etc.) are used?

Be original Brush Bare Escentuals' are of sable hair (of course), but are mostly rather rough. Is there a reason why use it? Is stronger / better for polishing rough?