Ditto Dat!!!Sorry peeps but I disagree with the approach of trying to super disinfect the brooder for THREE week old chicks.
Let's look at an unsavory fact about our fluffy butted friends: chickens EAT POOP! They do NOT live in a clean room environment. Trying to disinfect a brooder that just sent out 10 week old healthy chicks is not good. Chicks need to build immunity. They can only do that if exposed to the flora and fauna in small doses. Sterility can actually be the enemy here.
Just my two cents.