Fast 90 is fine, I use it whenever possible.
However, it isn't always possible.
My advice is to go to
hitman's Kriegsmarine Whiz-Wheel thread
(here:
http://www.subsim.com/radioroom/showthread.php?t=114351 ) and build one for yourself. It's pretty easy: You simply print out the three wheels, and pin them together:
If you want to get fancy, you can make the reverse side also.
Then download
klh's instructions for how to use it, found in this thread:
http://www.subsim.com/radioroom/showthread.php?t=126824
With a little practice, it's pretty intuitive to use and it helps you become deadly accurate.