For future reference, the majority of the time, you won't need to "flush" your cooling system. Flushing would be for if you had major crud build up (perhaps from a severely overextended coolant drain interval), or an oil of some kind in there. Modern coolants are some amazing stuff. Never have I torn into a healthy cooling system on a modern vehicle (like doing a water pump or thermostat) and found anything but clean, protected metal. No rust, no gunk.
I always get kick out of these people that flush with this chemical or that chemical, or even straight water to "clean" out their (healthy) cooling systems, especially when they're changing it far SOONER than the OE recommended interval, when the reality of it is that their cooling systems are already spotless and properly functioning.
If you still wish to change sooner than the OE recommended interval, then simply do a drain and refill with the OE coolant. Doing that is quick and easy and will help ensure your additive levels are replenished.