That would most definitely be easier if you use a Post Object field rather than a relationship.
With a post object you’d need to do a query, for example on the state page, to get all the counties
// assuming this is on the single state template
// $post->ID represents the id for the state post
// this only works with a Post Object field
$args = array(
'post_type' => 'county',
'posts_per_page' => -1,
'meta_query' => array(
'key' => 'state',
'value' => $post-ID,
),
)
$query = new WP_Query($args);
see WP_Query http://codex.wordpress.org/Class_Reference/WP_Query
for using a relationship field Eliot has a tutorial here http://www.advancedcustomfields.com/resources/querying-relationship-fields/
