The only thing I've gotten to work to keep sections dynamic on my pages is Ajaxize.
You have to wrap the section in your own function and place that function in functions.php and the functions have to output valid html but it is pretty simple.
For example, I'm using Login With Ajax and that needs to be dynamic to reflect the current logged-in/out state of the user.
So, in my functions.php I have the following:
function my_login_function() {
get_sidebar('loginwidget');
}
Then in Ajaxize in the wp-admin, I enter 'my_login_function' and it gives me an ajaxized div to place in my theme...something like this:
<div id="ajaxize_this:my_login_function:79676894d7c218aada82775fa0d5ed6d947b654a"></div>
I also use it for my shopping cart so that it stays current across any page.
Until I found Ajaxize I struggled with dynamic caching but this has worked perfectly.