At first you need to configure the DNS Servers in each domain for enabling the network connectivity between the domains.
Next step is create the trust relationship between the domains,
After creating trust relationship, you need use ADMT to migrate users, computers etc between domains.
To export the password of AD User Accounts from one domain to other, you need to install Password Export Server(PES) on the source domain.
Checkout the below link on Creating Trust Relationship, Configuring ADMT and PES installation,
http://social.technet.microsoft.com/wiki/contents/articles/16208.interforest-migration-with-admt-3-2-part-2.aspx
Checkout the below link on Configuration for SID History Migration and Use, Group, Computer Migration,
http://social.technet.microsoft.com/wiki/contents/articles/16621.interforest-migration-with-admt-3-2-part-3.aspx
To disable the SID filtering, please follow the below steps
- Login to target domain and start the command prompt with runas administrator
- Execute the below command to disable SID Filtering on target domain
For example, if your source domain name is green.com and target domain is blue.com,
Netdom trust green green.com /domain:blue /quarantine:No /usero:administrator /passwordo:Password1
Where usero, passwordo indicates the administrator credentials of source domain.
Once, you have executed the above command, you will receive SID filtering is not enabled for this trust.