A short test drive but it was overheating so I turned the car off?

This car started overheating excessively last year. The water/antifreeze was getting into the oil leaving the oil a light cappuccino color on the dipstick, white cloudy steam was also coming from the coolant tank and behind the engine where the plugs are, and out of the exhaust pipe. We stopped using the car because we thought we couldn't fix the head gasket and didn't have the money for repairs. It sat for almost a year and then we found out about "Blue Devil" a gasket sealer you use for a blown gasket fix. We had the oil drained already. We Took the thermostat out, followed the directions and flushed the radiator 2 times, and also put oil back in along with some engine flush. We applied the gasket sealer just how it said to and let the engine idle with the heater on high for a while before it started to overheat at about 40 min. Into the idle. It was supposed to run for 50 min then a short test drive but it was overheating so I turned the car off. Checked the oil and it was the same whitish brown. Since the car was sitting for a long period of time before we did this process, is it possible that it needs another round of gasket sealer to work? Will that help or is this an impossible fix, meaning unless I take the engine apart to get to the gasket it will run good again? Please Help!