Okay. I actually have two techniques. These were developed to deal with getting shots in my spine (actually, selective nerve block injections to the interstitial spaces around the nerves injured by my herniated disc).

One technique is straightforward: if it's phallic, and it's penetrating you, then there you go. Not only is it penetrating you, but it's doing so to put good stuff in you or (it helps to be into vampires here) taking stuff out. I've also used straight-up pain play mentality.

Also, I have a non-erotic method which is thinking about the thing deep inside (such as the nerve buried in my back) that needs help but isn't easily reached, and how wonderful it is that there is a thing--a rescue device, if you will--that can skip past most of the cells (and most of the matter, if you think at a quantum level) and can go right in to help this flesh-locked thing. That works for injections; maybe not so much for blood draws. I can totally get a claustrophobic panicky feeling about, say, the arthritic toe joint that cannot be reached any other way, and the idea of the thin rescue machine relieves the claustrophobic feeling.