With the release of Genesis 2.1.1 their is an additional ready to go widget that sits just below the end of each single post, this is a great location for an optin form or reader message that needs to be added to the bottom of each post.
This was previously possible but with a custom widget area registered and positioned.
To enable this widget area, you need to add one line of code to your functions.php file
add_theme_support( 'genesis-after-entry-widget-area' );
The widget is named After Entry and will be visible in the Widget Areas
And on the page the area is just below the single posts:
Add your content in the widget and you are done.