I have a Blick Studio Synthetic brush that is quite stiff (#6 round). They claim “these brushes retain their stiffness in water. They are also less susceptible to the ravages of acrylic paint”, which I find to be true.

Worth a look.

http://www.dickblick.com/products/blick-studio-synthetic-brushes/

blick-economy-white-bristle-flat

It is a good workhorse brush. Lovely firm brushstrokes, no loose bristles, and easy to clean. Even though they are white, I haven’t had staining problems with them.

I’m new so I can’t post links. Sorry.

Another brush I adore is Black Gold Dynasty. I use them with watercolors. Soft, supple brush and has a good spring. Holds better than my sables.

I can vouch for the silver brush bristlon.

If you want a brush that mimics a natural hog bristle brush, the absolute best synthetic bristle brush I have ever used is the Princeton Synthetic Series 6300. It has all the stiffness of real hog bristle but none of the drawbacks. It will not get soggy and soft in water or water-based paints and it holds its shape so you can maintain tight, neat edges and create great brush strokes. It will not get splayed out and ragged like natural hog bristle brushes do.

Another choice would be the Robert Simmons Titanium series of brushes. They have somewhat finer synthetic bristles and are a bit softer but they are great for control. They handle either acrylics or oil paints with ease. They are my personal favorites.

Both brushes are a little pricey but they will last for years.

Beverly