it works with armies that you can send out completely. If I send out my troops, I still have thousands of ballistas and reapers in stock that keep me in the negative. The best thing I do is keep thousands of Hussar on hand with fallen and longbowmen to carry back large loads.
The spy thing works fine, I have 10k spies sittin in the bush! =)
We wont need many spies until PVP time, but I have them ready. you only need 1 spy to do your spying or searching.
Oh and don't use spies to look at counties, use a raiding force of at least two troops, one long and one short distance. you will live past one round and get a full report, minus the wall defenses.