Kolibear
Just reading your second paragraph. I may have misunderstood you but dead cut is not referring to turning the both mags off, instead you are checking briefly that both mags are at least working.
I think engine handling is best learnt in your own share - cos then you get it right to keep down on the maintenence bills!
One more point - don't forget to check each mag before shut down - and watch the RPM to make sure it drops a little (50rpm or so), this shows that the mag will not be live when you shut down the engine, always a bonus if your about to pull it byt he prop!
Bodie