Madara most likely had many subordinates in many different places, but he probably didn't tell them the whole story when he sent them out to get information. When there was something of the utmost importance that needed to be discovered immediately, Madara would be the one to do it, because if his pawns knew too much, that could become dangerous for Madara. Someone might reveal information, and Madara's identity would be revealed to all the great nations. They would assault him relentlessly as a result. So you are right when you say he never shared power or knowledge with his pawns, perhaps aside from Itachi. Madara did say that a few vital secrets he kept from Itachi were the reason he was still alive; otherwise he would be dead. But even still, where Madara gets his information is a mystery; he must have very close tabs on everyone he needs information on. He follows them for a fair amount of time, and then when the time is right, decides to execute plans that have been in the making for quite a while, considering the amount of time he has.
