In my past used vehicles I ran a 3k OCI of SuperTech 5-30 with 7-8 oz. of Seafoam in the crankcase (1 oz. per qt of oil) - but that's it. They were used/neglected vehicles, so I just did the flushes once per vehicle, with the Fram Extended Guard filters (higher quality than regular orange can and well, WM backs their products for 3 months/3000 miles so that's a win-win there lol..). After the 3k, back using regular Pennzoil Conventional and ST even other OCI.
As far as the various "flush" products no never went down that road, they seem too harsh. I know many dealers even have TSBs regarding "power" (mechanical) flushes and other "strong" solvent flushes.
I wish I would have gotten one of those vehicles used oil analysis done....but when I intended on mailing the sample in, the vehicle got totaled - BUT, on the other hand, the front end smash revealed a good part of the engine; and it looked fairly clean.....not salvageable though in any way though.