The NRCS is correct in that you need to be patient with the native planting. During the first 2 or 3 years the native grasses are establishing their root systems. It's not until that 2nd or 3rd year that you will start to see the results or your labor. Until then you need to do some weed control. Check with the NRCS on optimal timing of mowing in your area. Once established, a rotational burn plan will create more diversity in your plantings and help maintain the warm season grasses. If you want more forbs in your fields, you can always seed them in later.