I recently switched to a Dremel for shortening my dogs' claws (or nails). Prior to that, it took two people, one to constantly feed treats, the other to clip each nail with a standard nail clipper. When the dogs saw the clipper come out they would try to hide. Quicks were nicked on occasion, making the process a nerve-wracking one for both the humans and dogs.

A good friend was over for dinner and I was telling her how much I hate doing the dogs' nails. It's incredibly important though, because my dogs are out hiking every day and a nail that's too long can be torn, which is a nasty, painful injury. She suggested I try using a Dremel and gave me some advice on which one to buy and how to use it. Off I went the next day to Home Depot and purchased the base model, corded Dremel tool. There are fancier, cordless versions, but the base model works just fine for this purpose. There are also other brands of this type of tool. While they would likely do the job just fine, my experience is with a Dremel so that is what I am writing about.

If you are going to try using a Dremel, I highly recommend you introduce it to your dog very slowly and wear safety glasses. Here is my step-by-step process:

Start by getting the tool out, unplugged, and let your dog sniff it. Feed treats when he/she shows interest in it. That's it for day one.
Day two, get the tool out, let your dog sniff and feed treats for his/her interest in the tool. Try touching your dog's paws with the unplugged tool and feed treats as the tool touches his/her paws.
Day three, repeat day two. If your dog is doing ok so far, recruit a helper and while they go into the next room and plug the Dremel in and turn it on, feed your dog treats. For this step, you may wish to up the value on your treats so they are especially tasty.
Day four, repeat day three. Remember to continue to touch your dog's paws, including nails at this stage, with an unplugged Dremel.
Day five, repeat day four. If your dog is doing well at this stage, plug the Dremel in near your dog and turn it on while feeding treats simultaneously.
For the next several days, repeat until you can turn the Dremel on right next to your dog and he/she does not react negatively to the tool. Continue to reward this behaviour with treats.
For the next several days or sessions, turn the Dremel on right next to your dog, have a helper hold your dog's paw and gradually move the Dremel closer to the paw while feeding treats. Do not touch the nail at this stage.

Just a few taps with the Dremel is all you need!

The next step is to begin using the tool on your dog's nails. You may wish to have a helper for this stage, just in the beginning. Turn the Dremel on and while your helper feeds lots of high value treats in succession, lightly tap one nail with the tool. If your dog is cooperating but his/her body language is indicating unease, end the exercise positively with lots of praise and treats. If he/she is ok with one nail, do a few more, but that's all. End the exercise for the day with praise and food rewards.
Gradually build until a) you can Dremel all of your dog's nails in one session and b) you can lessen the amount of treats you need to feed down to just feeding a treat at the end for a good job done. This will take some time and it is important not to rush through this. It has taken me about six weeks to get to this stage. It may take longer. Be patient and it will be worth it.
Remember to only do a few taps on each nail as the Dremel works very quickly. If your dog's nails are quite long you can Dremmel every other day or so taking the nail down just a tiny bit at a time, until they reach the length you want. Once the nails are at the desired length, maintain using your Dremel as needed.

When I get the Dremel out, all three of my dogs run to the dog bed we always trim nails on and try to muscle each other off the cushion so he/she can go first! When it is Stanley's turn, he sits on the cushion and hands me his paw! What a difference! We've gone from stress, anxiety and hiding from the trimmer to thoroughly enjoying the process of trimming nails.