1.) when you first start the car, just let it idle for a minute at max.
then when you drive, don't rev it much, just dawdle along for the first 10 minutes.
even if the temp guage is at halfway, the oil in the engine and gearbox and diffs are still cold.
10 minutes of sedate driving is enough cause you change gears and stop and move and stuff.
2.) letting your turbo cool down is not an issue that you should be too worried about.
unless you are redlining down your street and come skidding to a hault at your house, there is no real need to let the car sit idling for more than 20-30 seconds.
if you've been giving it a good fanging, then just take it easy in the last 2 minutes of your drive home or work or where ever it is you are going to.
when you stop, by the time you take seatbelt off, collect your shit out of the car, and get out, it's been about 20-30 seconds, then turn the car off.
the bov turned the other way.
that doesn't make sense.
just put it the way it's supposed to be.
It actaully makes the car run better that way.
don't worry about damage to turbo blah blah blah.. with it connected and working properly, the car idles and runs better.