GUIskin global font size

Hello, im trying to change font size of my skin, but not of single/custom element like

 gSkin.getStyle("<style_name>").fontSize = blah;

but for entire skin

 gSkin.font

as far as i understand from this link it is called "global Font" and as far as I understand gSkin.font would return me Font class

So my question could be paraphrased into: How to set Font size? and why Font class doesn't have method

Font.fontSize ???