The Wet on Dry technique is helpful when achieving detail and outlining.
When I paint with wine I usually start with the outline using the wet on dry technique. This is also a step that I have to do over and over again in order to get those darker shades of wine.
The Wet on Wet technique is helpful when blending the wines or adding a soft background.
Try this with both the wine and the wine mix to see the difference in colours and shades.