If you’re working in the same physical space you can use a file storage server with RAID configured to meet your needs. Some configurations can make your transfer rates pretty high, even if they are more than 2 users. RAID is a technique in wich you attach more than 2 hard disk drives for specific purposes. In a configuration; half of the Hard Disks can create an automatic copy of all the data of the other half … but it will be not as faster. In other configuration you can “add” the speed and storage of the hard disks involved for faster performance but with the risk that if a hard disk fail, you may lose your information.
If you’re not in in the same physical space you can search for setting up a FTP, a kind of “private” server between you and your workmate. It could be as fast as your internet connection and the set up of the ports in your computers.
Hope know you didn’t have serious bottlenecks due to the transferring files… it must be a headache. Wish you find a solution very soon !!