Define excerpt length by inserting read more tag

Question

There is a build in meta box to handle custom excerpts. You just need to check the excerpt option box under screen options in your post screen, once checked, you will see the excerpt editor box below your WYSIWYG editor metabox.

For custom post types, make sure that you set the excerpt as support feature in your arguments when registering your post type

'supports' => ['excerpt'],

WordPress will use your manual excerpt if set above the default excerpt calculated to 55 words from the post content

EDIT

I have quickly searched how to to add the read more link to manual excerpts in Genesis, and came up with the following solution (Thanks to wpmayor.com which states that this solution is compatible with Genesis)

function manual_excerpt_more( $excerpt ) {
    $excerpt_more="";
    if( has_excerpt() ) {
        $excerpt_more="&nbsp;<a href="" . get_permalink() . '" rel="nofollow">[Read more]</a>';
    }
    return $excerpt . $excerpt_more;
}
add_filter( 'get_the_excerpt', 'manual_excerpt_more' );