If you find a torrent with the exact same files, yes you can seed without downloading first. What I do it's to start the new torrent so it create the files. Pause the torrent. Overwrite the created files with the files I already have. Then verify the torrent. And finally resume it to seed.

1. You can try creating a torrent with the file(s) you have at hand and try to search with the info hash. You need to be sure the metadata (e.g. name, size, directory stucture, etc.) of the file(s) in question is identical to the original download.
2. You can try adding the torrent into a client. Pause it and then copy the file(s) to the download destination. Rename the file(s) accordingly. Ask your client to recheck/rehash the file(s). If the file(s) is/are identical, it will work.

Is there a way to find the torrent directly from metadata on the files or some other way instead of having to search on sites until I find it?

Yes and no. You may have some luck using a torrent search site with DHT crawler to see if it managed to index the torrent hash you are looking for. e.g. BTDigg, Bitsearch, etc.

But that's only one piece of the puzzle, if the torrent swarm is dead (no seeds/peers) then the torrent hash alone is not very useful. You require a .torrent file to reseed dead torrents. So without a .torrent file you'd better hope the torrent you are looking for still has some peers on it.

I would recommend considering Fopnu, Soulseek, ed2k, and DC++ as alternatives for sharing. It's only opening the program, choosing the folders to seed and that's it.