As with using the Notio, the MyWindSock web-based application produces results for you without you having to do the analysis.
If you are limited to using an out and back route and don’t want to invest in a Petot tube device, then using MyWindSock can be the best option.
You still need a power meter and a speed sensor on the bike, ideally a magnet-based speed sensor on the rear wheel.
You need a testing protocol so that you can collect data in a meaningful way.
You save the file, upload to Strava, and link your MyWindSock account to your Strava account.
You set up two Strava segments, one for the outbound section and one for the inbound section. MyWindSock will calculate a CdA for each segment, and you then take an average of the results.
You can repeat the test segments to get more results which will help with making judgements about which configuration is the faster.
Bear in mind that power metres and speed sensors only report to three significant figures, so don’t expect the CdA to be precise to four figures. Power meter accuracy is usually quoted as one percent. What we don’t know is if that is a random one percent for every reading or if all the readings are one percent out consistently. Environmental conditions are variable day to day and on the day e.g. air density, temperature and rolling resistance. These changes need to be accounted for. Don’t expect absolute CdA values. What we are really interested in is comparisons. For example is helmet A better or worse than helmet B.