Displaying Obfuscating Stupidity efectively.

One of my main characters utilizes Obfuscating Stupidity to get the upper hand, how do I play with this trope without making it look like an Idiot Hero with Ass Pull smarts.

Let some things drop through. Maybe he reacts with a BIT too much anger when no one else has figured out how bad of a situation they are in.

Have them be a bit more snarkish, or condescending when they are not with the other people.

Have him make mistakes in his act.

For example, my Dad knew a guy who was a skilled guitar player, but liked to sucker people into 'teaching' him how to play guitar. However, even though the result sounded like a beginner, his hand position was like a skilled guitarist. A perceptive person might have noticed that.

stealing that.