Sarah’s Pet Sitting recommends a short 4 foot leash like the Kong Traffic Leash, which has a handle at the human’s end, as well as a handle close to the dog’s end. This allows for better handling and maneuvering in tight spaces and on the street. A shorter leash keeps your dog closer, and prevents your dog from building up the kind of momentum that could result in him breaking the leash, or tripping his dog walker.
If your dog is blind, deaf, or nervous around other dogs, SPS recommends that you provide a leash cover/sleeve so that others will know to give your dog some space. http://dogsinneedofspace.com/gear-and-tools/ is an excellent resource to find something that will work for you and your pet.
Sarah’s Pet Sitting DOES NOT recommend retractable leashes, and may not be able to walk your dog on a retractable leash due to safety concerns for your pet and your dog walker. Retractable leashes can cause injuries, some so bad as to require amputation. If the clip breaks while your dog is a distance away, the recoil has been known to cause eye injuries as well as face lacerations.