Moving from RHSM subscription to Foreman (katello)

In my company, we have already a subscribed environment in RHSM, but we want to migrate to Foreman. We now have fully working Foreman and we need to import manifest. In Rh portal, we can create organization, but we cannot assign all subscriptions, as clients are already subscribed directly. Now the question is. Should we unsubscribe from RHSM, download manifest, import into foreman and then register clients to foreman? Or is there any better way to have all the subscriptions in Katello (manifest)?
Thanks