FFF,
I had exactly the same problem visualising why the AoA increases with sideslip. Even on my FIC the explaination didn't give me that warm fuzzy feeling inside of understanding.
Then I read the book "Stick and Rudder" which uses a view from infront of an aircraft at a slip angle to demonstrate the same thing as a the A4 paper method.
It's what I will use from now on for explaining it to students.
I work on the principle, If I can explain it withought me feeling like I am bullshi%^ing
I understand it.
FIS.