I'm currently using 1/2" (30 gauge!) on the outside lateral portion of my thigh. I just slip it in and push - hard on the plunger and hard on the syringe.
If its not going in my muscle, I don't know where else it could be. lol
I would much prefer a longer needle and bigger gauge but they don't sell them at stores around here anymore so Im stuck with the insulin crap. They work, only hassle is drawing a 5.5 ml satchet into syringes. It takes about an hour.