Don’t think I could do ED injections... I sit down with knee bent to do quad injections. Put the palm of your hand on your hip point your finger down like a gun. Basically anywhere the end of that finger is a good spot. Sit, draw imaginary line down center of your leg, do the same on the outside, half your quad from knee to hip, anywhere in there is generally good to go.
Keep in mind you do have nerves, veins, blood vessels in there. I pinned quads exclusively for a year. Yes I had issues at times. I did a few months ago started pinning delts for other places