You'll never do it. This season is a perfect example. I know of at least 14 friendlies from this season that are not in the handbook.
Want proof? One of them is here:http://www.arsenalprogrammes.com/arsenalhomes.htm
scroll down to England Youth
The others that are missing are: Barnet, Carshalton, QPR, Walton & Hersham, Cambridge United, Charterhouse School, Cambridge University, London University, RAF, St Mary's College, Grammar School, Tottenham and Friern Barnet (the last two being in a youth tournament).
You need to trawl through programmes, newspapers and programme catalogues, and then 20 years later when you think you've got them all you'll go through those newspapers again and find half a dozen more that you missed first time around.
The 1984-85 handbook lists 18 friendlies played during 1983-84. It doesn't list 17 others!
And it's not just reserve and youth team friendlies that are missed out of the handbooks. 1977-78 John Pratt's testimonial and 1980-81 against Kent County FA XI aren't in the handbook.