I like the MMO for the last few hundred miles of the oci. I've also used LiquiMoly 500ml flush, and would do so again. I'd also consider Kreen for a neglected engine.
If your doing the cheap flush with the QS, I'd run it a week or two.
change the filter, add half a pint of diesel fuel to the oil and run for 10/15minutes. drain it all out, refull with cheap bulk oil and run for 10/15 minutes.
drain the cheap stuff and fill up with good stuff