Hi again, Guitar,
If you do a little searching here, you'll find all kinds of tips & tricks -- some of which will change as the war progresses. It's actually not hard to throw the DDs off your scent in '39-40, esp. in deep water. One accessory you'll want, if you haven't got it already:
SH3 Commander. It's the icing on the GWX cake!!!
Stay alive!