Hi,
I have forwarded this case to the lead developer of the component. I now see why you were having issues. Currently, the style will only get applied if it is added implicitly, but like you said, this is an issue if you don't want 2 buttons to have the same theme. I will forward you his feedback as soon as I receive it. Also, if possible, I will provide you with a solution. I am not saying there is one, but if there is, I will give it to you.
Marc
Developer in Technical Support
Xceed - Multi-talented components - http://xceed.com