Unfortunately, your theory about the spillproof funnel working better because it keeps the coolant level above the engine is not valid. If air is trapped somewhere in the system, it won't find it's way to the radiator/reservoir opening any better than if the funnel wasn't present. In fact, it can make the fill/bleed process slower than simply pouring directly into the opening. The only advantage to that funnel is it keeps things a little neater with respect to spillage. Parking the car on an incline is indeed the best way to bleed air from the system. Filling the system SLOWLY is another important technique.
Unfortunately, your theory about the spillproof funnel working better because it keeps the coolant level above the engine is not valid. If air is trapped somewhere in the system, it won't find it's way to the radiator/reservoir opening any better than if the funnel wasn't present. In fact, it can make the fill/bleed process slower than simply pouring directly into the opening. The only advantage to that funnel is it keeps things a little neater with respect to spillage. Parking the car on an incline is indeed the best way to bleed air from the system. Filling the system SLOWLY is another important technique.
Thanks. I will do the incline method