Anyone have experience flushing the cooling system while the radiator is out of the vehicle?

I'm in middle of swapping out the original radiator at the moment. The top cracked, as they do, so I couldn't do a flush in the usual way of running water through it w/the engine running & heater on. I've also got the thermostat out since I'm replacing that while in the vicinity.

Is there any reason not to emulate the 'typical' flush by running water through it (via the top inlet) with the engine is running & heater on high? -- Aside from the obvious safety considerations such as keeping fingers and such away from the spinning bits, of course.

I'm also thinking a chemical flush may be in order. There was a bit of gunk around both ends of the top hose that has me a little concerned. It doesn't look like rust, but I could be mistaken. I'm like 63% sure the last time around orange stuff was used instead of the red Toyota stuff. Needless to say only the official red juice is going back in this time.

It is definitely good to get rid of all of the orange stuff. I'd try to flush w/ distilled water (98c/gallon) instead of tap water if you can swing it. Calculate roughly how much distilled remains inside the engine after the flush (probably about a quart) and mix the concentrate accordingly.

Get one of these for your garden hose. Then remove one of your heater hoses, and put it on the end (use the clamp that was on the heater hose). Turn on the water, and let run out the lower radiator hose until it runs clean.