How to paint according to qStylesheet in QStyledItemDelegate

I want to subclass QStyledItemDelegate and modify it with QStyleSheets. I dont have any clue of how to get it to work. I tried plenty of hours to just display anything, looking like I defined in the qss. In priciple it has to work, because when I call the base class implementation of paint(QPainter*, const QStyleOptionViewItem &, const QModelIndex&) the list items look like defined. Well, now how can I apply the stylesheet in the delegate?