I haven't played around too much with the trade route settings, as last time I accidentally set up a route between one of my planets and a port in another sector rather than between the two ports, thus wasting a few turns and losing a bit of cash. However, is it possible (and if not it seems like a useful idea) to set up a trade route between a Special and a planet? Even with a Level 20 hull I can only shift 300,000-odd colonists onto a planet at a time (same with fighters and torpedoes), so automating the process would be useful if you want to quickly get a planet up to speed. Likewise, it'd be handy if you could tell the trade route system what to trade at each end of the run - if I'm realspacing between a Goods port and an Ore port, I don't want the game to automatically sell all of my energy reserves at either end in case I wind up out of energy in a fight...
Special: Go to the special system and create a new trade route from that system to your planet. Energy: Go to "Global Trade Settings" and change the energy setting from "Trade" to "Keep". That's also where you can change your settings for the special port/planet trade route.
I also use Trade Routes to transfer Colonists/Torpedos/Fighters between some of my more developed planets, and some lessor ones. The same controls that determine what is traded between Special Ports and Planets also control what is traded between two Planets. It's a great way to never have to pay for a Colonist again.
Coupla my planets have kicked off into a steady population increase. I'm just interested in getting the rest there to boost the interest I make on the money.