I just would run it and bring it close to them and wouldn't let them run - they would sniff it and that would be enough for now. A couple hours later or even the next day I would do it again -- patiently -- and put it away. Then try with one toe and if the dog is ok, another - if he/she gets anxious then stop for the timing being.
It works great on the little dogs but it didn't work well on my big dog. It wouldn't take enough off and would actually start to smell like it was burning. It does work to smooth things out a bit after they are clipped though. You might have better luck though, who knows.