Why is he refusing? Have you tried a “change of face,” like getting someone else to ask him? Maybe he wants a man to assist him, and he’s feel uncomfortable with a female helping. Perhaps you could also set a “date” and say, “Dad, we are going out tonight, can you go get showered and ready?” Also, what time of day did he shower in the past? Morning or night? That could be throwing him off if he’s a morning shower person and they’re asking him at night.