I have done the battery replacement on 3 retina 13" MacBook Pros and it was very easy.
I don't like using any kind of runny liquid inside any computer. To "cut" the adhesive bond between the battery and top case, I used thin, braided, nylon string and gently dragged the string from top to bottom of each cell in a sawing motion. After this, I removed the remaining adhesive by using a cloth that was lightly dampened with rubber cement thinner.