Add a "read more" link after both manual excerpts and regular excerpts in WordPress.

functions.php

<?php
//* Add read more link after both manual excerpts and regular excerpts
add_filter('the_excerpt', 'amn_manual_excerpt_read_more_link');
function amn_manual_excerpt_read_more_link($output) {
	global $post;
	return substr($output,0,-5).'... <a href="' . get_permalink($post->ID) . '">Read More</a>.</p>';
}