How can I find someone quickly?

If they are in your Corps, send resources to them and follow the line. If they are in another Corps, try having a farm or an alternate account that belongs to you join the Corps of the person you're looking for and find him that way. If the person you are looking for is not in any Corps, you will have to search the map to find him. I would suggest having everyone in your Corps help you if that was the case.