EMLA (lidocaine and prilocaine) or LMX cream
These creams contain local anesthetic
which will numb the skin after 15 - 30 minutes.
Apply cream where shot or IV needs to be placed and apply a tegaderm (type of bandaid). Tell yourself, or the subject if not you, it will be over in an instant. Take a deep breath and "bite the bullet". "there, it wasn't all that bad, was it?".