There are always problems using the Trace functions! Can I suggest that you use the "Shades of Grey" profile when using Trace. Then use Expand then ungroup your trace results from the object menu to convert it into many vector shapes. Then use the Layer Panel to find the shape background that is white and remove that. You can go on and remove other artifacts that are unwanted as this is the problem with the tracing results.
If I was in your shoes and if the glass was a relative simple shape I would simply draw it an manually give your shape the Opacity that you require and this shouldn't take long. Please remember that you have Gradient fills that you can use and since you have CS6 then you also have Gradient Strokes which are very useful in this area if you use one of the Artistic Chalk and Charcoal brushes from their library and I would also give these strokes opacity. Also you have the image that you want to copy so you can sample colours from that when choosing your gradient.