The Trade Goods business....

I can't seem to understand the trade goods.
Sometimes I'll find a Trade manager and there's nothing loaded on the horse or the cart.
I have stuff in my bag, but that's not good enough.
I can give it to Carl, but he doesn't seem to do much with it either.

I really didn't enjoy driving the cart so I wondered if there was an automatic function for this? (I've done the honey run with Yann)

I feel like I have a grip on most of the other aspects of the game.
I'm on Chapter 9.
I've been playing about 100 hours.
I'm working towards getting the money to do the Pailune Counsel Upgrade (by completing the security jobs).

Any help gratefully appreciated.