Tarmach
Speed, distance, time. You time how long it takes you to fly between two points, then, using the DST formula you find the average ground speed. You then compare this to your airspeed. This will tell you your head/tailwind component.
Once you have your groundspeed, and know your drift, the rest is relatively straight forward to do on your wizzwheel.
A little long winded I know, but you did ask.