Orderby two meta fields not working

SPECIAL THANKS TO THIS ARTICLE: http://dotnordic.se/sorting-wordpress-posts-by-several-numeric-custom-fields/

$args = array(
  'post_type' => 'property',
  'tax_query' => array(
    array(
      'taxonomy' => 'rc_repl_status',
      'field'    => 'slug',
      'terms'    => 'sold'
    )
  ),
  'posts_per_page' => 100,
  'meta_key' => '_rc_repl_property_year_sold',
  'meta_query'  => array(
    array(
      'key' => '_rc_repl_property_year_sold' // do this to order by two meta field VALUES
    ),
    array(
       'key' => '_rc_repl_property_acres', // do this to order by two meta field VALUES
    ),
   ),
);

// do this to order by two meta field VALUES - This takes generic values and
// can be used with any WP_Query meta_query
function customorderby($orderby) {
  return 'mt1.meta_value DESC, mt2.meta_value+0 DESC';
}

// Now apply your filter. Add it before your query and remove it 
// afterwards to make sure it doesn’t affect subsequent queries.
add_filter('posts_orderby','customorderby');
$query = new WP_Query( $args );
remove_filter('posts_orderby','customorderby');