Answer:
I hide but my head is outside.
A harvest sown and reaped on the same day in an unplowed field. Which increases without growing, remains whole though it is eaten within and without. Is useless and yet the staple of nations.
Hoofed frolicking.
Many hear me, but no one sees me, and I only speak when spoken to
If you happen to wear one of these warm garments around, you might get doused in red paint.
You use it between your head and your toes, the more it works the thinner it grows.