I have Dremeled my dog's nails since he was a pup and there is no better way to do it. However, this item is cheap and weak and runs through batteries. Just do yourself a favor a get a Dremel that will do the job well in the first place. It costs a bit more, but is well worth it in reliability and saved aggravation. The one you want is the Dremel MultiPro Cordless 7700-02. (You don't need the 50 accessories that come with it for your dog's nails, but I've only seen it sold that way and that's how it's sold on Amazon.)
The two keys here are that it is a 7.2V Dremel so it is much stronger and better suited for large dogs, and it comes with a rechargeable battery pack so you don't have to replace batteries. Plus, you'll have a real Dremel around the house and you will definitely find other uses for it once you have it. Although the MultiPro may be more expensive initially, you will save money in the long run. Trust me, you'll thank yourself for getting the better tool.