Can't change size of brushes.

Make sure your caps lock key is not on! That's all it takes. Thank goodness for YouTube! 

I had the same trouble, had to resize my tools pallet for these options to be displayed

I know that this might have been answered in another post and the last post is a bit old, but it's still unanswered so...

First, the Properties windows for brush DON'T allow to change the features of the Brush tool! If you want pixels/Type/Scales/Cap/Join option, you can only the pen tool.

To change the Brush tool options, everything is located at the bottom of the tool window (where you select the Brush tool).

Those options include :

Draw Object, Lock Fill, Brush Mode, Brush Size, Brush Shape, Use Pressure and Use Tilt

Draw Object, Lock Fill, Use Pressure and Use Tilt are "activate" options where you use them or not.

Brush Mode, Brush Size and Brush Shape are drop down button that let you choose different options.

Have you Darrel or anyone else figured this out?  I'm running CS5 but am having the same issue.  I've tried restarting Flash and everything but for some reason the slider and text box in properties for changing the brush size are faded out.  Also I've tried using [ and ] but no luck! I've tried messing with a few things but just can't seem to figure it out.  Any suggestions?

Thanks!

In the tool-properties area you can change the size of the brush. This area is located at the bottom of the tools pallete.

A note, though.  The brush in Flash doesn't work like the brush in Photoshop or Illustrator.  In Flash, the brush draws in reference to the screen, regardless of the zoom level, rather than following a pixel size.