As a general rule: Women , girls and young boys tend to need more “vocal cord closure” so “nasty” sounds or hard consonants such as ‘g’ and ‘k’ and more open vowels such as ‘oh’ and ‘ah’ are a good idea. A man’s larynx (and a boy’s whose voice has changed) tends to go up as they try and move up the scale. So it is a good idea to use “hooty” exercises with narrow vowels such as ‘ee’ and ‘oo’ to try and encourage the larynx to stay down as the pitch ascends.
However, because of trends in the pop music world where women sing low, in recent years we do see more and more young girls that can’t seem to get out of their chest voice so they need to be handled more like a male voice. In order for a singer to be able to move up the scale without “letting go” two things have to happen, #1, the vocal cords need to thin to get the higher pitch, and #2, the larynx needs to stay down. So it is important to try and determine which of these two reasons are the major cause of the singer not being able to move up the scale and address it first. If the reason the “chest puller” can’t get into their mix is because they are trying to pull up too much vocal cord, “nasty” exercises can work for them as well to help thin the cord while keeping cord closure. This will only work if the larynx is not rising too much however. If the larynx is rising significantly it doesn’t matter how thin the cords are, they are still going to need to learn how to keep the larynx down first before they are able to mix into their higher range.
If a woman, girl or child is not getting enough “cord closure” it is best to work them in their lower range. If someone is trying to drag up too much vocal cord it is best to start higher in their range, forcing a release of some kind, then moving lower. Remember narrow vowels such as “oo” and “ee” are better for “release” and more open vowels like “oh” and “ah” are better for holding on to more chest.