HI Often I have a situation when you cannot get off from your wagon because you are near NPC and it is automatically selected.. So I have found a magic combination, S+R (you should basically hold back and get off from the wagon) and voila, you can get off from a wagon and go to a trader you need I hope it will be useful for someone
I agree that it is not the most profitable but barter requires attention, and I like trading while watching movies and doing my stuff