I use the guillotine type too as have found as they get older their claws get thicker and the scissor type just don't do the job. I try to take a little off at a time as frightened of getting the quick. Having said that its easier said than done if your dog won't keep still! (Hence why I'm getting the vet to give Darcie's a good trim while she's being spayed on Friday!)
Our vet nurse will always do their claws for a small donation to one of the animal charities that they support, so if you're unsure pop Mollie along to your vet and I'm sure they'll help you.