How can I train myself on air reccé in my spare time?
Read lots of magazines about aircraft and look at the pictures. try to find pictures of different variants and study the difference. Try to look at unlabelled pictures of aircraft, try to identify them, check the answer then study why you were wrong.
Maybe build some models.
If you can get hold of some copies of Recognition Journal, read those. Follow the techniques using different source images.
Plenty of good Facebook groups and pages dedicated to aviation, join those and enjoy the posts!
Are there any official documents or sample images?
Believe their are some on Ultilearn, but nothing amazing!
If you have the time you could always laminate aircraft pics with the answer on the back. Or as it’s been said join some aviation related facebook groups. This is a good page to start off with: http://www.aircraftrecognition.co.uk/ I’m sure if you use my best mate google he could offer you lots of other pages to look at.
I’ve never seen it before, when they do the competitions and the like do they just use stock photos of the aircraft in flight? Are they always nice clear photos? Up close or away in the distance?
There will be a mixture of close and distance images, both on the ground and in flight. The higher the level of competition, the more difficult the image will be to discern.
When I used to work on the setting of competition at regional level; where the answer required was a generic type e.g. Il-76 CANDID or Tu-16 BADGER that was often a distance shot. If specific a variant was required, e.g. Il-78 MIDAS, the view would be closer and from an angle where the identifying characteristic is visible.
There will always be one at Wing Training Day and if your sector does one then there will be one at Sector Training Day.