"Cuban Motion" is, without a doubt, one of the most difficult stylings of Latin dancing...Much harder than any step pattern! Think of it as something you will work on "forever". There is no instant fix. It will continue to get better, and it also change, as you become more advanced.
In teaching Cuban Motion most teachers use what I call "crutches". Things that will help the student achieve the proper motion in time. Bending and straightening the knees, rolling from the inside edge of the foot to the outside edge, or the hula hoop example, all help and are part of the whole action. The end result is what you see the professionals doing in competition.
Chris Morris (former United States Champion) explained it with what he called the 8-count system. I have had excellent results with it while teaching students. It is again just a crutch in order to learn, but it may help.
8 Count Cuban Motion
The normal count of a measure of music is 1,2,3,4. This is counting the BEATS of the measure. In between each beat there is a “sub” beat. The 4 beats could be counted as 1 & 2 & 3 & 4 &, or 1,2,3,4,5,6,7,8, counts. Try listening to some strict tempo Rumba's to hear the 8 counts.
The hip movement is caused from using the muscles in the area of the diaphragm or midriff, rather than using the knees. This is also sometimes called “rib cage” motion. (However, the knees' do bend and straighten.)
When you do the “eight count” Cuban Motion, you never Step and move the Hips on the same "count". Start with one hip already "out" and the body "settled".
Step on 1 (no hip movement) … “Squeeze” the Hip on 2,3,4
Step on 5 … move Hip on 6
Step on 7 … move Hip on 8
This must be practice slowly at first, and then build up speed.
Start by just walking forward. Then try it in the Rumba “Basic”.
Oh....and by the way...GOOD LUCK!!