Have you tried offering to buy ore from miners?
Try your best to make a guess at how much it's worth, then make a payment offer.
Then, even if you have no clue where it is sold, you can make guesstimates.
Mining stations would not buy ore, but processing plant's, smelters, depots, and industrious planets would.
Even if you're not selling at the best place, you're making a good profit considering you got the ore for pretty cheap, or should have, directly from the source.
Now, to actually answer your question, yes i know a few routes.
Which house does your trader live in, if in a house at all?
Edit:
This also...
' Wrote:What ID is your trader using? Believe it or not, that's very important to what route you chose...