Vista glass, I did this myself. Had green went pink.
I just bought 10 gallons of distilled water for the flush. After the first one, the second came out mostly black (in the bottles). I bought another 5 gallons and flushed it again. Seemed to be hose particles. Which is why I replaced my main hoses and will repalce all the front hoses when I add my center radiator this fall.
It is a pain to fill and drain while still on stands and there may be an air bubble or two. I always had to do multiple fills during the heat cycle venting procedure as descrribed in the bently manual. I bought the uView 550000 because of that and used it for my final fill. When I have to flush it again - will for center radiator if nothing else - I'll use the uView to make my life easier for the flush and fill cycles.