Production Plants (White Giant)

My enterprise Global Wealth currently owns 22 production plants, however I can't get it to use them when building corps, my corps take quite a while to build as they are waiting to production plants to become available, how do I get it to use the production plants I already own? also is there any way to change the automatic order for production plants when you order the building of a new corp as I would like to change them to immediate orders. Thank you for your help.