I actually delete all the items in the theme's css file, and then load a seperate css file. I do this for 2 reasons. One I load the 2nd custom css file from a CDN to make it perform better, and I want it loaded on the bottom of head items. Q2A is very easy to manipulate through css, almost every element has a class or an id associated with it. I have been able to get Q2A to match my existing site's structure with a few days worth of css.