Princeton Brushes - Snap! Series Talkon Brushes
These are nice little 3x0 watercolour round brushes, as good as any, for making dots, hairlines and signatures on your oil paintings.
I like this little 1/4 Angle shader as well. It is good for working on very small paintings and pulling to slightly smudge pigments within a flat glaze. Any bigger, and this filament would not be strong enough for oils.