Managing group policy from a different forest

I have two domains set in the environment in two different locations. We want to use one Domain admin account and be able to manage both environments. What would be the best practice to assign the group (builtin administrator account) to the second forest to be able to manage all group policy objects? Currently we can manually add a builtin admin account from the 1st domain to Delegation section for each group policy object. Is that the recommended way? any way to allow full access to the whole forest?