radiator removed – is it still possible to flush system?

I’m replacing radiator and a/c condenser on my car. After hitting a deer, they both bent inward and most of the coolant leaked out of the car.

I got both of them off the car and realized I forgot to actually flush the system with distilled water while the old radiator was still on.

I also have the thermostat out so would be a good time to flush; however it would be a pain to connect the old radiator back on with the transmission lines.

Is it necessary? If there’s coolant still in the system it isn’t much. But I know it’s probably not great to try to flush after installing new radiator, so I’m trying to see if there’s something I should do now before installing the new radiator and condenser.

I should also add that I did not remove the water pump drain plug, so I don’t know if there’s more coolant in the system. But since the radiator was empty, as well as the reservoir tank, I can’t imagine there’s much in the system.