The notepad procedure wants it that way because it uses ID to tell the stadimeter how high the real ship is to calculate range. With that range, and your estimate of AOB, it can figure out what the actual movement is going to be between begin and end of the speed measurent, based on how much the scope moves. This makes speed, the most important value for leading, very dependant on the other values.
There are other ways to determine speed. And all the other values. Taking care of one value at a time is much easier to calm your nerves.You don't even need the notepad to enter them into the TDC, you can enter it directly on the F6 page. But you need to switch the TDC to manual before, and back after, entering the value in the dial(s).
My preffered way for speed is to let the target pass my periscope line. The length from the recognition manual divided by the time it takes (in seconds) can be used to calculate the speed in meters/second. Knots is roughly twice that. But you need to steer a certain course such that your speed doesn't influence the result.
Speed procedure:
1. Set periscope to 0 or 180 degrees. Only look along (or backwards) your direction of movement. Then your speed doesn't matter.
2. Turn uboot until periscope is right infront of the target's bow.
3. set rudder amidship (turning is taboo!)
4. Wait until the bow touches the line and start the stopwatch.
5. stop the stopwatch when the stern/aft-end clears the line.
6. Divide length by time, double that value to get knots.
7. Enter speed in knots into TDC speed dial.
But if you plot on the map, you can figure out his course and speed at the same tiime. You just need to do it at known intervals. But with the nomograph this is piece of cake.
AOB depends on where you are in relation you him. So that changes all the time. But if you project his course into the future (based on some plots not too close together) and at some point in time you take a (relative) bearing and plot that (as true bearing) on the map, the intersection with the target course shows an angle that you can measure using the protractor. With the scope pointing to the target you enter that AOB in the dial.
Even better is to just turn 90 degrees across that target course and wait for the target to approach. As you wait you set the periscope to 0 or 180 (depending on forward of aft tubes), and set AOB to 90 (needle pointing in direction of movement through scope). When the TDC manual/auto switch is back to auto , just pointing the scope takes care of the right AOB. Just take a last range reading and enter it in the TDC before you shoot.
Plotting tutorials:
http://www.subsim.com/radioroom/showthread.php?t=90234
http://www.paulwasserman.net/SHIII/#Section II - Manual Charting While Moving