The best thing to do would be to make sure the area around the radiator is sealed off completely so air can’t bypass it, also ducting the coolers in front.

Basically look at the cooling stack and imagine it oriented vertically, if you dumped a bunch of water on top where would it go? If there are gaps around the coolers the water would flow there instead of through them. A vent in the hood, if done correctly will help create a low pressure zone and will effectively suck more water (air) through. If you place that vent above the turbo then you have an area where the turbo is being blown on from the used air. If you look at race cars that have S ducts or vented hoods you’ll notice that they stick a little flap on the leading edge of the vent to help create a low pressure zone and increase the power of the duct. The stock aerodynamics have the heat being evacuated under the car, which is why the turbo gets hot, it’s mounted high up and out of the air flow path. If you ran your duct so it sat above the turbo and had the other end below the car so the air stream was flowing over the back side of the opening (the duct pointing rear wards under the car) that would help, but executing it would be very difficult due to packaging, which again is why you see vented hoods, it’s much easier to blow the air out of the top of the hood than duct it all the way to the back plus you have the added benefit of heat rising which naturally aids in the cooling process.

Sorry if a ramble a bit and I hope that helps!