This is not possible in the current implementation.
Afair Adobe scheduled such an improvement in the next major version, probably Flex 4.
If your problem is limited to a small number of components, you can write a helper method taking a UIComponent and a list of style names in parameter. Using the styleManager.getStyleDeclaration you can easily apply the styles to the component passed in parameter.
Ok .... ... I will wait for Flex 4 then....!!