If you have never changed the coolant (it has a 2-3 year life), then you might drain it, fill it with straight distilled water, run it till hot, let it cool, and drain. Do this a couple of times until the water comes out clear.
Otherwise, a like for like coolant, the Toyota Red Longlife coolant and distilled water, with normal change intervals, would not need a flush. Drain and fill back up with new. Use the block drains to make sure all of the old is replaced with new.