This is how I do it now:
$this->redirect('validate_failed', 'Coupon', 'coupons', array('coupon' => $result, 'filename' => $filename, 'message' => 'Expired.'));
avoiding the whole flashmessage thing and passing a other stuff I want as well.
and this is my couponcontroller method that catches that redirect:
/**
* action validate
* @param Tx_Coupons_Domain_Model_Coupon $coupon
* @param string $filename
* @param string $message
* @return void
*/
public function validate_failedAction(Tx_Coupons_Domain_Model_Coupon $coupon = NULL, $filename = '', $message = '') {
$this->view->assign('coupon', $coupon);
$this->view->assign('filename', $filename);
$this->view->assign('message', $message);
}