Wow 200????
Yeah you really want nothing left at the very end and it is living off the stored food. That is why the leaves curl up and shrivel at the end.
It really depends on the strength of your soil.
I have run Hydro or even dead soil that ran on fertilizers and that is easy to flush. A few days or maybe a weekish in the soil.
With a great compost it really wont be easy to do. But start over watering by about 3 weeks before the end I would say.
I say that becasue I play it by ear. Normally I water once a weekish. In a good soil I may add tea every 2 weeks, in a great soil I may add nothing. So over water as in get a ton of run off until the water is clear each time and I start watering every 3-4 days near the end.
With those small clones I really only ran water after I got them started so what does it even mean to flush right?
So it kinda depends. But you wont really get a great flush with a great compost.
That is the rub.
You can spend money and put in a lot of time and effort and run a premo hydro setup that allows for optimized control including a fabulous flush (honestly probably the best benefit IMO). That takes a lot more effort , time and money...but the final product does taste a bit better. I don't want to argue...I have grown both I know all about both. I like growing hydro too. Doing soil this way is about the easiest way to grow weed by far. There is some up front labor but as you saw once I got to the state of perpetual cloning at about 6 months I could have maintained a water only once a week regimen on those mini clones. untreated once a week water is about as easy as it gets.
Properly cured, good soil grows wont make you cough. The curing is the most important part. It makes up for a lot and a poor cure kills a lot of great weed.
I will do hydro again. It is fun.