When Scouting always use full attack
Scouting is done through either going into the rally spot and selecting scout as shown below or when you are on the map selecting the desired target (e.g. another players city, NPC, or Valley)
As stated in the leadership formula normal heroes can only lead 110k troops effectively. This applies to scouts as well. So when sending scouts to scout a player never send over the 110,000. Of course if u have the uprise buff full this increases to 182,000. The problem with scouting is that if the opposing player has about 800,000 scouts or more it can take millions to get a successful report from him. If he has a Historic Hero in defence it can be nearly impossible to get a report from them. Scouting can also be easily fooled by bluffing and if you are attacking a player with multiple waves scouting between each hit it can be extremely hard to figure out just what you are killing.
In both attacking and defence in scouting the most important thing is to have your honour as low as possible, 0 if possible. This will ensure that you get the highest wounded proportion possible. And make your city very costly to scout. This can prove a deterrent to many players who don't want to waste millions of scouts on you getting a report. Many players will not continue to attack a player if they can not find out how much they are killing with their waves.