My very favourite brushes for inking and stencilling are the contour make up brush.
There are two types I use:
These ones are the normal contour brushes - when choosing them, you need to look for a very dense head, this will make all the difference in your blending. If the fibres are too loose, you will not get a great result. The more fibres pact into the head and the firmer the head, the better.
I use a lot of different types of brushes depending on what my project needs are - the above brushes gives a smooth effect where other brushes I use can give stroke lines or texture to my piece.
I did not purchase any of these brushes from craft stores - all have been bought either online (aliexpress) or in retail shops such as Kmart, TKMax, Target etc - shop around, you will be amazed at the saving you can get.
Some examples of using these brushes: