After the many failed attempts at making a wax model. I have decided to go with plaster. Here is an image of my plaster model. I did this only once and to my surprise, it was a success. For this mold, I used foam core again. This time it was easier since the plaster was cold and wasn't going to damage the mold like the wax did.
With this model, I played with positive and negative space. Interestingly, this came out a lot nicer as compared to my earlier wax trials.
Here's another view of my plaster model.