Hi there, I'm actually have an OpenWRT device in my parents house with an USB which I access from outside trough FTP by No-IP DDNS.
With FileZilla I send them media files from my house to them to the USB and then, my parents play those files trough DLNA without any trouble.
But use FileZilla is..... as slowly as posible, and I'm thinking about use transmission to directly download files to theirs USB but, how can I access transmission from outside?
FTP shouldnt be any slower than a torrent, if there's a difference in speed it's because of the router not being able to handle the traffic, the media you're writing to being slow or your own internet connection unable to saturate theirs.
Transmission doesn't provide remote upload services and it doesn't support adding custom peers.
It can download using only BitTorrent or Magnet links published on trackers.
In any case, set up a VPN and you should be able to reach LuCI and Transmission web-interface.