Can I give files (via usb) I have previously downloaded to someone else so they can seed them and help improve their ratio? Do they need to re-download the .torrent file or will giving them my .torrent file work as long as it's from their IP address?
Give them the video files only and they can put them in their torrent download folder. They have to download the .torrent file logged into their own account. When they add them to the tracker it will read the file and seed if you have done it correctly. I did this to help someone out and I have also done it myself with videos from other sites when I didn't want to keep seeding there and the same video was here. I will tell you the person I helped by setting him up with an account and making it easy for him to get off to a good start with his ratio didn't really appreciate the trouble I went to.
Be careful NOT to share your .torrent files with your key and also make sure that person is not using the same IP address that you are using.