To be honest, I use Thrudds as well and can find good routes pretty easily. (800-1400 per ton of trade cargo) I do keep a log, and sometimes get the scoop on an even better route, (1700+) but they are often few and resource dependant.
Two things I did find REALLY helped my bottom line were:
1) range, The fewer jumps between ports the better. It basically translates to less time in transit = more $ per hour
2) a good fuel scoop.... invest in one. I currently have a 3A which does 176/s. This means I can usually completely re-fuel after a 22 Ly jump while positioning my ship to point at my final port destination. (circling the sun) Little lost time, no fuel costs.
So in my trade equipped asp (112 T cargo space, with a bare bones shield and a 22 ly range) I can get around 268,800 cr in a round trip.
A->B, one jump, 1200 per ton * 112 tons space = 134400