Dealing with Zend Auth Data when using zend modules

Question

I am working on zend module based structure for my project. As Zend_Auth class' default session storage is Zend_Auth. I changed according to module being called. Say for admin I use auth namespace Admin_Auth and for default module i use namespace name Default_Auth.

$auth = Zend_Auth::getInstance();
$auth->setStorage(new Zend_Auth_Storage_Session('Admin_Auth'));

I am doing this because, if I do Zend_Session::destroy() it will destroy complete session even for Default Module. and so using namespace and so at logout Zend_Session::namespaceUnset('Admin_Auth');

each time in different controller I have to use

$auth = Zend_Auth::getInstance();
$auth->setStorage(new Zend_Auth_Storage_Session('Admin_Auth'));

just to point corresponding session data.

I am considering to move it in module's Bootstrap.php like

protected function _initAuth(){

    $auth = Zend_Auth::getInstance();
    $auth->setStorage(new Zend_Auth_Storage_Session('Admin_Auth'));

    return $auth;
}

First, is that proper way? Second, If it is then how can I access the return value $auth of _initAuth() in each controller? Please