How long was the orange "Kool-Aid" in there? If not long, change the thermostat & gasket, cuz that'll be next. Flushing the system should get any lodged crud outta the heater core (remind your wrench to flush that side too, not just the engine). If you've had that orange GM junk in there for say 30,000 to 40,000 miles, plan on intake gaskets sometime in the future. Longer than that? Start thinking head gaskets. Not wanting to rain on your parade bro, just telling you what I've seen happen. Had a GMC truck in my shop that was born with Dex-Crap in it, and at 64,000 miles I had to put new heads on it. It's got good-ole-green in her now.
On a sideline, I've had really good luck with the Prestone "yellow" (looks green to me!) "mix with anything" stuff.