If you install a masonry chimney, you don't need to sweep it for ash. The fly ash from anthracite will fall into the cleanout and can be vacuumed out. The ash will only accumulate in horizontal sections of flue pipe.
A stainless steel chimney should be swept to reduce the acidic action of the ash on the stainless. A ceramic chimney will not be affected by the acidic ash.
Hope this helps. greg L