Certified signing and Smart Installer

I have a Symbian application written with Qt.
It must have Certified signing (because of the capabilities).
And it must be packaged with smart installer.
How should I sign it?
Can I create a sis with my application, package it with smart installer and send it for Certified signing?
Or should I send for signing only package with my application, get it signed and after that package it with smart installer and publish to Nokia store with Express signing request?
What is the right way?

Basically you would pack your application into sis, certify sign it, and then wrap it with smart installer and express sign this sis.