Can mechanical agitation increase the reaction rate?
If the reaction is heterogeneous (multiple phases involved), mechanical agitation helps. If the reaction is homogeneous (all reactants and products in the same phase), mechanical agitation usually does not help. An exception is when the process is auto-catalytic (i.e. starts in one corner and then propagates).

In the example mentioned, agitation will help to transport concrete away from the brick surface and to bring fresh acid to the surface. Scrubbing also helps if there is no chemical reaction and the removal is mechanical in nature.