How do you style TextFlow with CSS Styles in Flex 4.5.1?

I would like to be able to style a TextFlow element with styles defined in my CSS file. My current TextFlow implementation is shown below but changes to my styles do not seem to take effect. How would I style TextFlow with CSS styles in Flex 4.5.1?

// In defaults.css
.textHeader
{
    fontFamily: "Trebuchet MS";
    fontWeight: normal;
    fontStyle: normal;
    fontSize: 25;
    color: #FF0000;
}

.textBody
{
    fontFamily: "Trebuchet MS";
    fontWeight: normal;
    fontStyle: normal;
    fontSize: 12;
    color: #525252;
}

// In MySkin.mxml
<s:RichText left="5" right="5" top="5" bottom="5" id="richText">
    <s:textFlow>
        <s:TextFlow>
            <s:p styleName="textHeader">
                Cupcake cookie cotton candy chupa chups biscuit marzipan. 
            </s:p>
            <s:p styleName="textBody">
                Cupcake cookie cotton candy chupa chups biscuit marzipan. 
                Jelly beans cake jujubes. Powder cotton candy apple pie applicake. 
                Bear claw powder dessert macaroon.
            </s:p>
        </s:TextFlow>
    </s:textFlow>
</s:RichText>

I don't think you can do this. At least not easily. According to Adobe, TLF doesn't support CSS style declarations:

http://help.adobe.com/en_US/flex/using/WS02f7d8d4857b1677-165a04e1126951a2d98-7ff2.html

However, you might find 3rd party implementations that work:

https://dev.c-ware.de/confluence/display/PUBLIC/Flex4+Text-Flow+and+CSS-Styles

(I haven't tried it myself).