Greetings, basically with one hand being more in control of the poi as you mentioned its usually just a case of being more dominant with one over the other as in right handed verses left handed etc.
Try when learning say for example to do a weave once you get it mastered going forwards then learn backwards as that can be applied to many routines as it then helps make whatever hand is less coordinated catch up to the other.
If you take the time to concentrate on the planes or circles that you are spinning so that they are as tidy as possible for very basic twirling it will definitely help further down the track when learning more advanced routines.
I guess really its just a case of practice practice and more practice.....
Viewing the footage on Poi in the free lessons will also help.