Hi
If you had the same issue as that article, you would not see the set-cookie response - as in that issue the content of the logout.html page is never sent to the webserver it is retrieved from the local client cache - and so the webserver never has the chance to send the set-cookie.
So if your seeing a set-cookie for LOGGEDOFF then you are past that issue!
But that set-cookie should replace your existing SMSESSION cookie - it can fail to do this if the domain= sections are different than the original set-cookie domain for SMSESSION.
And on your next request to the protected resource it should send the SMSESSION=LOGGEDOFF to the server.
But if you are still able to access the resource, then it will be cached or if it send the older value for SMSESSION then the set-cookie command to LOGGEDOFF didnt work.
But the latter steps in the fidder should show what is happening.
Cheers - Mark