There are no special tricks or techniques when it comes to painting a still life other than a good sense of observation. Study your subject and try to focus on important visual elements that characterise it. In the case of glass, it is transparency. The most important thing to keep in mind when painting any subject is to let the work evolve. Here are some process images from my last post that show how the glass bottles came into being.
1. The basic forms are drawn with paint and mineral spirits and colours are blocked in. The focus is on getting the right shapes and tonal relationships.
2. I continue to block in the colour and focus on tonal relationships. The interesting thing about coloured glass is that the cast shadows take on the colours of the subject which they would not do with opaque objects. The shadows are also seen through the subject. This is what creates the sense of transparency.
3. At this point, all of the colours are blocked in and I can start to refine the tonal structure. I will also apply paint in a thicker fashion.