That was my purpose in hooking up the garden hose to the system. The core, with the chemicals was never hooked to the whole cooling system until after a good flush. I even reversed the hose so I’d backflush anything out, before reconnecting the core to the system.
I wouldn’t want to use a “flush kit” with these chemicals…knowing some of it would migrate towards the engine itself.
Hooking up to a flush kid DOES NOT close the passage to the engine itself.
Unless you’d crimp the hoses toward the engine with a visegrips or something.
Besides the radiator is new, the coolant is new and clean as a whistle. Why contaminate the radiator and coolant with whatever you disolve. I’d rather disolve whatever is there and not allow all the disolved crud into the whole system.