Wiping After Poo?

How have you taught your kids to wipe their butt after they poo? My son is almost 7 and he still needs help wiping, to the point that we always check after he goes. We’ve worked on using adequate toilet paper (not just once square lol) but how to I help him understand that you have to wipe as many times as it takes to get clean. Going through the motions just to say he wiped leaving him still dirty. I appreciate any advice!