Configuring sharepoint to consume identities from multiple domain active directories

Hi,

I am trying achieve below things.

1. Allow users from external domain "ExtDomain2" to get automatically logged into Internal Sharepoint application hosted in  "IntDomain1" from "Ext-D2-Machine2" machine without entering credentials.

Question: Is it possible? If yes how to configure?

2. Allow users from "IntDomain1" to get automatically logged into sharepoint application without entering the credentials.

Question: Is it possible? If yes how to configure?

3. If 1 and 2 is not possible, if user enters his credentials first time while accessing the sharepoint application for the first time that is also fine.

After doing search in the internet i have learnt that, I should make Sharepoint 2013 as claims aware application and install ADFS on both the domains and configure sharepoint to trust ADFS1 and ADFS2 .

I have configured below lab. 

Good explanation/ Pointers will be very helpful.

Currently with the configuration i have, Users from both the domains needs to select there identity provider first then provider credentials to login into the site.

mallikarjun