If you are opening with it: a feather, and take far longer than feels necessary. The point is the waiting, and almost everybody rushes it.
If you want one piece covering the whole range: a pinwheel. The same tool is a tickle at light pressure and sharp at firm, so you can move through the range without swapping toys.
If you would rather not hold a handle: gloves. The sensation follows your hand, which makes it easier to stay connected and to read how somebody is responding.
If someone is nervous: start on a forearm, not anywhere interesting. It shows them what the tool actually does, and it takes the alarm straight out of the pinwheel.
On blindfolds: buy one with whatever else you get here. Removing sight is the cheapest way there is to make everything on this page work better.