How do you change the main font used in all of the containers? I have tried editing the portal.css, default.css, skin.css, container.css and associated ascx files. The only change that I can make is the font color, not size or type of font. I have seen several workarounds on the forums, but the default font type, color and size has to be assigned somewhere.

What is the most expedient method to accomplish this?

In the container.css file you can set any of the font properties ..

for example..

.ContentPane .normal {
    font-family: "Courier New", Verdana, Arial, Helvetica;
    font-size:  11px;
    font-weight: normal;
    color: red;
}