So I have actually done this tutorial, the finished product is adorable, I have been giving them to my neighbors with clippings from my garden. There are a few things I have learned along the way:
1. Do not use a glass with any etching or print on the sides, the design will show through no matter what.
2. A 12 oz cup requires a 17 inch balloon. I assume an 8 oz cup requires a standard balloon. I had to go and find jumbo balloons because mine kept ripping.
3. Be careful puling the latex to hard, I went through about two balloons per vase. I found using two butter knifes to wedge between the glass and latex helps the shimmy-ing process.
Overall this is a totally cute and simple project that looks professional!