There's a workaround for Painter for lag problem maybe.
-Pick up a flat brush, say the the ink pen "flat color" variant. -In the General brush controls menu under Dab Type, drop it down to Blend Camel Hair. - If you aren't happy, reset the brush in the brush menu but don't save over it.
That way, you got that camel hair blend, but with a brush that isn't so hungry for your resources. This is what I did before I got a way better computer. It worked well and actually helped with coming up with various techniques.