Go to a professional groomer. Trust me on this, your dog will thanky you for it.
I ended up cutting poor Aggie up a few times when I tried. She's a Golden Retriever and so sweet, she didn't even cry-although she was bleeding from all the spots I cut her at. You have to be trained to shear an animal. They got all these nooks and crevices.
A groomer costs about $70 but it will last you the whole summer. You'll pay for 2 shearings with the $150. Make an appointment with a groomer.