i cheat when i do rolling circles but this will help. Start with standerd rolls. as you know, you need to put some down elevator in when your inverted. well do two rolls. get the feel and get it so that you dont lose any alt. then do three. when you can do it all the way acrossed the field then your ready to get it to turn. What i do is when the plane is knife edge i give it more or keep the elevator cammand in to get it to scribe the circle. try a 180 turn. if you can do 180 turn while rolling than you can roll acrossed the field, do a 180 and roll acrossed again. The last 1/4 of the circle is the hardest just couse it looks funny. it took me a weekend to learn this way.
After you get comfertable do them then you can learn the rudder cammands and have them perfect.
I think this is the best way becouse you learn one step at a time.
Hope this helps.