If you can find it, Understanding Performance Flight Testing: Kitplanes and Production Aircraft by Hubert Smith takes up where Askue's book leaves off. Unfortunately, it appears that it's out of print and is currently being sold at a scalping premium price. BTW... Askue's book is great with taxi tests, envelope expansion and flight characteristics, but barely mentions anything about performance testing. Smith has a chapter on the initial testing, but gets into a lot of detail on performance testing.
Essentially, you do the tests on a calm wind day, record the temp, altimeter and field elevation. The book gives you formulas that you can plug into a spreadsheet that will convert for different density altitudes and weights.
Doing the tests will be much easier with a video camera pointed towards the wing. The airfield I did this at had runway lights that were each 200 feet apart. I videoed the takeoff and landings (three in each configuration for averaging) and used that to come up with my figures. When figuring out the distances needed for the formulas, I watched the video and used the runway lights as a measurement for distance.
For the takeoff, you're essentially measuring your acceleration (how long it takes to pass each runway light). However long it takes to accelerate to your takeoff speed will determine how much distance you need. Landing is similar, but you're only measuring the distance from touchdown to full stop.
BTW... Due to the requirement to generate polynomial equations from the numbers you generate, Excel is probably the best spreadsheet to use.