Talkgroup ID's vs Wildcard

Hello all. I am new to digital scanning, so be gentle but I need input. I am in Ohio and we have the MARCS IP system. I currently have a wildcard object set up, so I am hearing everything. What I want to do is be able to hear only certain local agencies, but retain the wildcard for any foreign agencies that come into our area. I have locked out the agencies I don't want to hear. Now what I am thinking is to create objects with talkgroup IDs for those agencies I want to hear, so when there is traffic I get the hit and an alpha display. I would then l/o those local agencies on the wildcard, so the only thing I should hear on the wildcard are the foreign agencies. Does this sound like the best way to do it, or is there a better way? Do I have to enter separate IP system entries for each talkgroup ID, or can they all be off of one entry? If it needs to be separate entries, please explain to my why. As I said, I am new to this and still trying to learn. Thanks to all for your feedback.

Talkgroup ID's vs Wildcard