I think that depends mostly on the owner.

Some are more experienced then others and can feel the smaller follicles. Its probably one of those things you get better with once you know what you are looking/feeling for.

Also depends on the female, her muscle tone , how big she is, is she full of food.

I don't "feel" my females much at all, because I'm not sure how much pressure is "to much" and I don't want to hurt them. Sometimes I let them "slide" through my hands and I try to feel something, but no luck yet !