Using .install file with a feature

I have created a feature(user_password_policy) which sets configuration values for the password_policy module and the force_password_change module.  However, some settings are not picked up by strong arm so I need to make these changes with hook_update_N.  

Do I create an install file, user_password_policy.install?  If not, how can I do db updates in my feature?  

For the update function, do I call it 

function force_password_change_update_7100() {  In other words, do I reference the module I want to refer to in my feature?

function user_password_policy_update_7100() {  or do I need to use the feature name in the function name?

The function needs to do this:

  db_update('force_password_change_expiry')
->fields(array('expiry' => '0'))
->condition('expiry', NULL)
->execute();

I'm I on the right track?

thanks
Milton