For Cloud how do we migrate from legacy password hashes to new version?

For a standalone install we would either

a) login to back office, amend web.config to new settings and then save an updated password or

b) use a dummy install with same machine key & updated web.config settings and to create a new 'master' password; then update DB with this and use password reset feature to allow users to reset passwords.

Unsure what process should be for 'Cloud/Portal' linked accounts, we don't want to lock ourselves out!

Anyone have experience of doing this on Cloud?

For MembershipProvider we can just update web.config and issue new passwords either via back office or own 'Forgot Password' feature; it's the UsersMembershipProvider that we are not sure about.