## first in your functions.php add the following function

//Shortcode to show the module
function showmodule_shortcode($moduleid) {
	extract( shortcode_atts( array('id' =>'*'), $moduleid ) );
	return do_shortcode('[et_pb_section global_module="'.$id.'"][/et_pb_section]');
}
add_shortcode('showmodule', 'showmodule_shortcode');

## then create your single-customCPT.php file duplicating page.php from divi and look for line 45 :
the_content();

## and replace it for
echo do_shortcode('[showmodule id="YOUR LAYOUT ID"]');

## remember: you need to create your divi layout first.