How does ToolBar change the style of Buttons?

I'm trying to adopt the flat look of regular ToolBar buttons in a regular
stackpanel (can't get the damn overflow arrow to go away on my toolbar), but
even after looking at the various styles and templates for my ToolBar
instance, I cannot see where the button style gets set and therefore, I
cannot adopt the same style for my regular buttons. Could someone enlighten
me as to how the style gets set so that I can poke around and try to figure
out everything in the button style?

Well, I dug out Reflector and followed through a bit to find that it uses a
resource key called ToolBarButtonStyle for all regular buttons.
Unfortunately, {StaticResource ToolBarButtonStyle} throws an exception, and
{DynamicResource ToolBarButtonStyle} does nothing, but I'll still try a few
things/dig around a bit to see if I can gain access to the style as opposed
to just duplicating it.