What time of the year are you hoping to have the food plot(s) ready for? What is the ground you are planting like now, is it bare, etc?
In the right situation, broadcasting will work great. If you have bare ground now, then frost seeded clover in another month or so is really easy to do. Otherwise, what Letemgrow said is true for the rye and brassica seed too, but that would be planted late summer.
Although I have never tried planting sunflowers yet. I do have a bag of sunflower seed that I was planning on using this year though AND I have a spot mowed that I could easily hit with Roundup this spring. So I am curious to know more about how sunflowers can be seeded.