Whiz wheels are great for pre-flight planning but I've never attempted to use one in the air in a light single. I might be tempted to use one if the aircraft had a reliable autopilot and I had a passenger who could scan for traffic while I had my head down.
I was taught a rather neat method to assess drift, heading, ground speed and timings which doesn't overtax the grey matter.
1. Always write down the forecast winds aloft on your flight log.
2. If a diversion is required, plot the track on your map. Having a ruler with built in rotating protractor helps. Write down the new diversion track.
3. Using the nearest forecast wind for your altitude, calculate the amount of drift. If the forecast wind is 60 degrees or more off your track, allow 6 degrees per 10 knot of wind speed. For a difference of 30 degrees, allow 3 degrees per 10 knots. A wind speed of 20 knots would double these drift figures. A wind speed of 5 knots would reduce the drift correction by half.
4. Next, calculate the headwind component. A wind of 60 degrees off the heading is equivalent to half the wind speed. A 45 degree difference is equivalent to two-thirds the wind speed. A 30 degree wind angle is equivalent to 100% of the wind speed. Reduce or increase your TAS by this amount, depending on whether you're dealing with a headwind or tailwind.
5. IAS/TAS conversions aren't worth doing unless you're 6000 ft or higher. Then add 10% to IAS per 6000 feet. Calculate elapsed times using 120 knots ground speed = 2 miles per minute, 90 knots = 1.5 miles per minute.
It sounds complicated but once you've done it a few times in the air, you get faster and it works fine.