huī survives in modern Chinese chiefly through one compound:
麾下 (literally 'under the banner') = 'under one's command', 'serving in one's army', 'belonging to one's faction'. Used both in historical writing about generals (
韩信麾下 'under Han Xin's command') and in modern figurative business writing (
百度麾下 'in Baidu's stable of subsidiaries'). The verb sense 'to signal / direct troops with a banner' is purely classical and meets the eye only in historical texts.