http://www.westcoastpetsupply.com/1/dog-nail-care/why not try the normal nail clippers and take off what you feel safe doing and then use the electric nail grinder.they are good. i know its not what you origanally wanted but im a groomer and i would sometimes get it wrong too.
take off little by little and then file the edges i hope this helps.if its an concelation (cant spell it lol) i have never been happy doing nails they all grow differently.xxx
please feel free to tell me off if ive put a link on thats not allowed whoops