i mean really skinny in the sense we dont hand out with a belly, is a western thing isnt it? as hosseny said, fat is good sometimes in oriental dance.

Thank you Zamira. For all who aren't registered at bhuz, here is the answer of user David, who obviously wrote a book on ME dance technique.
"The shimmy Randa Kamal uses is the Reda shimmy - more known as the Raqia Shimmy or Jillina Shimmy. However, when Randa and I hung out at the Stockholm Bellydance Festival back in the days and she used me as a puppet to demonstrate the correct way to do things when people asked questions this is what I learned:
1. the shimmy is generated by the hamstring. When you contract the hamstring, it automatically pulls the knee backward. The hamstring will be fully contracted way before the knee joint locks or even straightens fully.
2. this shimmy takes quite a lot of strength training of the hamstrings prior to looking as excellent as it does on Randa.
3. Randa is reeeeeaaallly strong.
4. you have to relax your hip and lower body to generate this relaxed look. You especially have to relax your glutes and allow the hip line to move vertically.
5. you get a better result if you align your knees ahead, hip behind and chest square on top of your alignment axis/weight point in your feet and then tuck your abs in to open up the distance between the hipbone and ribcage in your lower back. This results in the typical forward leaned Egyptian posturing of the body.
6. think of pumping the movement from the floor through your hamstring and isolating it at the diaphragm.

There, that's a pretty simple explanation of how you may achieve the shimmy that Randa uses.

Just for the record, it's hardcore Egyptian technique - it's not Suhaila Salimpour Technique or a kneeshimmy or anything like that. It's a straight forward Egyptian shimmy with correct muscle work and alignment being the key to achieve the result.

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I hope this procedure of copying from bhuz is not against some unwritten rules...

this is encouraging!!!!
I cannot get my shimmy going "on command" - at all.
this has frustrated me a lot in the few classes I have taken (it sounds ridiculous - I was always known as the girl who s a great oriental style dancer in my family - and took great joy in dancing at festivities, but when I really wanted to learn the technique I was so horrible at it :) ), I have now begun to understand I probably simply have to start "little" and slowly, and persistently work at it at home...