Subdomain - Sharing Session Data Between Domains In Asp

i want to maintain session data between two applications or domains [URL]. I have read on net about this, but many people pointing many different ways to do it, with people commenting +ve and -ve responses to all. Plus many are just providing theoretical answer, do this and that ,but no code at all. are these steps all that is required?

1) in web.config: <httpCookies domain=".[URL]"/>

2) store session data in sql DB as:(after preparing the db for storing sessions)

<sessionState mode="SQLServer" sqlConnectionString="Data Source=YourServer;
Integrated Security=True;database=MySessionDB" sqlCommandTimeout="30"
allowCustomSqlDatabase="true"/>
<machineKey decryption="AES" validation="SHA1" decryptionKey="..." validationKey="..." />

3)Am confused about this one: i want to set the domain for the session cookie like this

Response.Cookies["ASP.NET_SessionId"].Domain = ".[URL]";
But where should this code be written?
this entry: [URL]says: use System.Web.SessionState.SessionIDManager as a base class but the SaveSessionID method is not virtual so cannot be overridden. Options are: either explicitly re-implement the interface method or decorate SessionIDManager class and after calling SessionIDManager.SaveSessionID set Response.Cookies[SessionIdCookieName].Domain to our domain.

Only if the author had provided real code, step 3 would have been clear. Plus all this 3 steps enough to share session among the domains?