Ask Mr. Smarty Plants

First, let me refer you to our page of How To Articles.  At the bottom of that page under LARGE SCALE WILDFLOWER PLANTING are several articles that apply to your question.  In particular, "Getting Started" suggests using a grain drill or a hand-carried mechanical seeder to sow the seeds. It may be possible that you can rent such equipment from a local nursery or farm supply store.

The "Meadow Gardening" article suggests that you add native grasses to your wildflower mix because:

"They provide support and protection for tall flowers.  They fill in spaces around wildflowers otherwise occupied by weeds.  They add color and texture to the landscape.  They prevent soil erosion.  They provide food and cover for wildlife."

"Meadow Gardening" also gives you tips about preparing the soil and what to expect for your field of wildflowers after the first, second, third years and beyond. 

In the answer to a previous question about seeding large areas with grasses, our Director of Landscape Restoration, Steve Windhager said:

"Hydromulching is a bad idea. The tactifier in hydromulch is actually hydrophobic (repels water) when it gets dry. As a result, most native seeds die when they are applied with hydromulch. Native American Seed has spread seed by hand and then sprayed on a "clean" hydromulch mix (no seed) for erosion control and they say that they have had good results. We are now recommending pneumatically applied compost for seed applications that would have formerly used hydromulch. It works GREAT, although you may have some leaching of nutrients (nitrate and phosphate) out of the compost with any run off, so you don't want to do this near a creek or river at this point."