paint something with a broad brush

paint something with a ˌbroad ˈbrush

describe something in a general way, ignoring the details: His description of national politics is painted with a very broad brush, although some areas are described in a little more detail than others. ▶ ˌbroad-ˈbrush adj. [only before noun] dealing with something in a general way rather than considering details: a broad-brush approach
See also: broad, brush, paint, something