Start SLOW... Dremel off, on the floor or wherever you'd like to do grooming. I do it in our family room because it's carpeted and comfy for both of us. First time it could be just having the dremel near, or if Remy is calm enough, just touching the Dremel, off, to each paw - treat. If nervous just do one. End of lesson 1. Do it again, and again, and again. I left the Dremel in our family room a few days, just sitting there so he could check it out. Then one day I started it - end of lesson - treat! Eventually I got to touch a paw with them Dremel on and so on....
1) go SLOW
2) give LOTS of treats
3) always make it a happy, exciting time
4) always end on a positive, happy, praise, treats
I have trimmers, but hate them. No better way to scare a dog off from nail trims than to hit a quick.