X52 setup

I have had the Saitek Joystick X52 for some time now, but I have never been able to assign some of the buttons, which is rather annoying. Is this a common error?

Also, do anyone have a good idea what to assign the slider on the throttle stick to?

All those buttons work for me.  The only button that that does not work is the pinkie switch below the the trigger. That could be used too  if I programmed all my buttons using the Saitek Joystick Software but I don't run that software; I just do it direct ie open the key settings in BoX and press the joystick buttons so the action is assigned to 'JS Button 4' etc.

I use the slider for brakes because it allows me to set a small amount of brake to make taxiing easier but that is mostly for use with red aircraft that are steered by applying brake & rudder at the same time.  By the look of your setup you appear to be flying Blue.

Oh I do fly both sides, and your suggestion to use it for VVS breakes is good.