I bought a copy of 'Diversion planning' by Martyn Smith.
A pleasantly slim volume with some easy calculations and handy techniques.
I don't think it matters what you use to work out the corrections one you've sorted out the direction.
Basically:
On the ground draw a wind vector on the chart where you can see it.
Choose you diversion point.
Draw a line no matter how wobbly. From the point of diversion to the destination.
Guesstimate a halfway point.
Stick your pencil on the chart along the line.
Slide your pencil to the nearest VOR and read off the angle.
(Highlighter lines on the compass rose make this easier, using a VOR takes care of magnetic).
Do the drift calcualtion, refer to the DI to double check. (e.g course is 170, wind is 100, you'll need to steer into wind so the number will be smaller)
Divert over chosen point.
Write down the time.
Measure the wobbly line with a suitable object (ten mile thumb, pencil with lines on it or try to retrieve the plotter you've dropped on the floor)
Now calculate airspeed the journey time and hence the ETA.
(Again use DI for reference, is the wind against you or behind you ?)
Check course and speed at halfway point.
Achieve destination and pass nav test.
Don't hesitate to use whacking great line features that point directly towards your destination.
Since the DI only allows you to fly to within say 2.5 degrees there isn't a great call for ultra precise calcualtions.
Worked for me anyway.
30.06