I would flush the system for at least 15-30 minutes, you can do it anyway you wish just make sure for this that the thermostat is out so you have free flow without worrying about temp. I see the dexcool horror's every week, and everyday on newer cars we service I see it and tell the owner, if you want to avoid repairs and seeing me much more often.....spend a few dollars and have the orange removed.
Green coolant is by far the only good choice. I have gone years with green and my rad,hoses and metal items such as water pump all look great and no corrosion or scale build up.