You know it's funny but when you say something like I get frustrated you're identifying a feeling with a label. Take it from there. Explore what you just labeled. Being in the head is a feeling, explore that feeling.
What worked for me was a variation of Paul's instructions. Instead of saying feel the colour of the feeling it was,'If this feeling had a colour what colour would it be?. If it had a shape what shape would it be?" and for getting a feel for the size the question I asked 'If this feeling has a size what sized/type of container would I need to put it in?' So if you get stuck on Paul's saying notice the... try changing it for yourself to the question If it had a ... what would it be? Now you are describing your feeling without labeling it. Now when I hear Paul my mind just jumps to the answers.
Alex