A drill-powered rotational brush apparatus features an electrically non-conductive tubular housing, and a metal input shaft rotatably supported in the housing has an external end reaching out from the housing for engagement in the chuck of the drill. A connection is provided between an internal end of the metal input shaft and a brush whose radial bristles reside externally of the housing at the second end thereof. The connection features an electrical insulator that electrically isolates the metal input shaft from the brush and any portion of the connection that lies externally of the tubular housing beyond the second end thereof, thereby protecting the user form the risk of electrical shock. The connection end of the brush matches the cross-sectional size and peripheral shape of the external end of the input shaft to allow coupling together of two like apparatuses to collectively form a longer brush assembly.