i do everything with the roller, the fenders and wheel lips all with the roller, the only place where the brush comes in is when doing the drip rail, the front cowl grill slots, under hood, trunk, door jambs. but even then for the cowl vent for example, i would run the brush in every slot, and then finish off with the roller on top. i also had a spray bomb on hand with the same color thinking i would need to spray a hard to reach area and never used it. even when you do the door jambs for example, i would say 90% can be done with the roller, and the rest you do with a foam brush, finish with the roller last.