We use flexslider 2 (http://flexslider.woothemes.com/) and use custom document types and repeaters to accomplish content sliders in Kentico CMS.
In the repeater web part, we use the HTML Envelope to put the container elements in, then use the transformation to repeat through the dynamic section.
We put this in the Content before:
<div class="flexslider"><br/>
<ul class="slides">
and we put the closing tags in the Content after:
</ul><br/>
</div>
Then the transformation contains this:
<li><br/>
<img src="slide1.jpg" /><br/>
</li>
Add the JavaScript file references to your page, specify the path to your slider documents in the repeater web part and it should work like you would expect.