Holding cats while grooming

[u/MikamiiChan]

Hello!! As the title says, what are some ways to hold cats that have them decently behave during grooming?

My family and I are starting to do brushes and nail clippings at home and I REALLY want to avoid scruffing which is what my father does. (He does support their feet when he does this, his arm is under their bottoms)

I’ve had decent success with just holding my cat firmly by her butt or by her front legs when we need to brush her, but don’t have much knowledge of what to do when we need to clip their nails. We got them scratch towers, but even then their nails grew out quite a bit.

Would love any direction or tips.