The airbrake could be partially extended on the ground (undercarriage down:rolleyes:) by using a test switch in the cockpit – we spanner wielders used the airbrake test facility to communicate between cockpit and spanner man when carrying out engine adjustments during a ground run – this was in the days before the headset and long lead were in common usage.
The gun barrels were fitted into the forward fuselage prior to the gun-pack being winched into position, and were then connected to the cannon, if my memory is still serviceable. Can’t remember how long the barrels were, though – not my job, I’m engines chiefy!

True, when using the test switch the airbrake doesn’t deploy to it’s fullest extent (only about 20 degrees I think) and then snaps back to the up position automatically.

Your memory is spot on, the gun barrels were disconnected from the front of the gun package to allow it to be dropped out. The barrels were then withdrawn from the blast tubes and stored in the gun pack trolley with their respective guns. As you say they had to be inserted into the blast tubes prior to the gun package being winched up into position. The barrels were not visible when fitted as has already been said.

Try the recently published SAM Publishing Modeller’s Datafile on the Hunter by Paul Bradley for all the info, colour walkaround photos, profiles, diagrams and accurate scale plans you’ll ever need to model one!;)