I tried a few (expensive) clippers especially for dog grooming after Valentino got a very unflattering cut at the groomer's about 5 years ago and have been clipping him myself ever since. But, with all those expensive clippers, I am most satisfied with the Conair clippers I found at K-mart. He has very thick hair and I find that the clippers work really well, especially if you remember to clean and oil them with each use. It is important to find one with a good, powerful motor too. That will also help. Good luck!
Conair.com - Personal Grooming > Clippers > Premium > Model Hc200gb