The generally accepted method is to drain the oil, change the filter, and install eight quarts of synthetic oil.

That's all the "flush" that you need unless the engine has been horribly abused.

Be advised that any "flush" will definitely provide significantly lower viscosity than engine oil, thereby running the significant risk of much higher than desired wear for as long as you run the engine with the flush. If you run the engine for one minute, the flush cannot seriously do much of anything. If you run the engine for two hours, the flush will do some cleaning............and you'll be without some cylinder, ring, and camshaft material when done.