One more point about the air bubble. It should be the last thing to leave the syringe. My Rebif nurse explained it to me this way - The air pushes all the medication out of the needle so you really inject it all. If it wasn't the last thing through then some of the medication would stay in the needle instead of entering your body. Also, when pushed out relatively fast, the air helps to move the liquid away from the injection site, thereby helping to prevent injection site reactions.
I also gave up the Rebiject after reading a post here last year about injecting "straight". I don't remember who it was, but they gave a couple of tips on how to uncap the needle. First, point the syringe needle-end up and make sure the air bubble is at the top (tap the syringe if you have to). Pull back on the plunger a couple of millimeters and pull off the cap. This prevents formation of a drop of the med on the tip of the needle thereby helping to keep the low pH Rebif from having direct contact with your skin (key to reducing site reactions). Then turn the syringe 180 degrees so that the needle points down and tap lightly to send the air bubble to the top, between the plunger and the liquid. Inject slowly and when you get to the air give a quicker push so the air will push the Rebif away from the injection site. You should be able to hear the air going in.
This method has worked very well for me. Other than red splotches, I haven't had any injection site reactions. Hope this help you to.
RRMS since 01/07.