I can't remember what I use for the buttons like the SubTool Master main one. I'll see if I can find the work files when I have a moment. But it's something bold and sans-serif with the anti-aliasing turned off. If you open one of the buttons in PS you'll see it's grayscale with the art on a layer. Like that it will take on the ZBrush UI colors.
For smaller icons I use the interface to generate the title I need. I make a custom menu and call it whatever title I want then I do a screen grab and clean up in PS. For those little titles you are editing on a pixel by pixel basis.