Here's my take on the turbo cool-down question:
The turbocharger actually takes very little time to stop spinning, or at least to slow down to a point where it's not a problem. (Maybe a few seconds or so.) The reason to wait before shutting down the engine has little to do with lubrication, and more to do with the fact that the turbo bearings are cooled by the flow of motor oil. The instant you turn off your engine, the flow of relatively cool motor oil stops. Whether the turbo is spinning or not, the temperatures inside the turbo are extremely high just after a high-speed, full boost run. Synthetic oil is an excellent choice in turbocharged engines because it can handle much higher temperatures without burning and forming nasty carbon deposits, which will ruin your turbo. (And the rest of your engine, too.) I think two full minutes of idling is MUCH longer than necessary! If you come screaming into your driveway at 90 miles per hour with the turbo at full boost, you might want to wait a minute for the turbo to cool down. If, like me, you spend a couple of minutes driving gently through your neighborhood at speeds barely above idle after you've left the main highway, the cooling problem is already solved and you can shut down immediately. Synthetic oil will take care of the rest. Just use a little common sense.
As for blocking the radiator, I wouldn't worry about it if you own a New Beetle. I think the flow of air through the radiator is close to zero until the cooling fan starts up. I'm not sure about Jettas or Golfs; they seem to have a more direct flow of air through the radiator grill.
-mickey