Oh, alternate idea - when you're creating contracts, where it says to enter the country you want to sell it to, have a block above that that lists your country/enterprise's corps that make use of the commodity in question. For example, when I click on my Soybean corp, it should list my Cattle Feed corp right above the search box, so I don't have to go digging for it.
(Also, if you're doing this, have the trade quantity default to the corp's 100% use. Why does defaulting to selling the corp 10x as much as it can use make sense?)