to Tesscorm --they say you are supposed to count to 10 after you press the button --so max 10 seconds to inject.
And a GI doctor WITH Crohn's ON Humira told my son it's the medication itself that is painful, not the injection --so that's why so many of these tricks--ice, buzzy, whatever --don't work so well. The medication is 'thick', she said, and very uncomfortable. Still, we let it sit out for an hour before injecting which we were told might help and he ices the injection site for 10 minutes beforehand.
My son prefers to inject in alternating legs -- and then can't walk for a 1/2 hour after. That said, my husband injects his Humira in his belly, no icing the spot beforehand, and is completely fine afterwards!!