The correct execution of CBM will happen naturally once you fully understands the concept.
I don't believe you will need to isolate and solely practice CBM. It seems that you are "manufacturing" CBM as a distinct body action that does not quite fit in with the the rest of your movement( when dancing figures that are described with CBM). No doubt you are experiencing a "twisting" of your top because you
are very conscious of CBM as a separate element that you have "added" to your movement. Perhaps because somewhere in some technical description it said that CBM is required on certain steps of a figure.(I know because I am talking from experience).

CBM will happen naturally if you swing correctly and make the required amount of turn. As you step forward or backwards you will swing both sides through but when you need to make a certain amount of turn over the figure ( or create a
side lead on the next step ) you will need to swing either the left side or the right side faster than the opposite side. CBM describes this early commencement of turn that results from this kind of swinging action even though the foot is traveling straight forward or backward.

So taking the Natural Turn of the Waltz as an example:

1.Your right foot is placed straight forward (relative to your body position).

2.As your weight moves onto the right foot both sides will be swinging forward but your left side will be travelling through faster than your right side so that by the time your weight is
collected over your right foot you would have made some turn. This is what is meant by CBM on step 1.

3.You will continue to turn as your left foot and left side swing through onto step 2. The movement that you initiated in the first step continues into the next step.

So CBM is an integral part of the total swing and turn of a figure. It is used to describe (and NOT ISOLATE) the early commencement of turn, by swinging one side faster than the other as both sides swing forward/ backward. If you get your swing and turn over the entire figure working correctly then your CBM will be correct. Don't think of CBM as a separate action.

As an example, think of the Natural Turn in the Waltz like this:

"As I step straight forward on my right foot I will commence and continue to swing my left side through (in a manner that is natural & unforced)
making a quarter of a turn to the right by the time my left foot is in position". Your CBM will be fine. Notice I say "swing my left side through".You will get the one side to travel faster than the other by feeling that you are
consciously swinging the left side (in this case) through in a natural & unforced manner.

You will find that the forward swing is initiated in the shoulders and the backward swing is
initiated in the hips.

Len.