All alone here, have done it so many times wouldn't trust anyone else, use sterile technique, aspirate, and know exactly where and where not to shoot. Which also depends on the gear, For example I can only shoot t-400 in my glute, too painful anywhere else. The needle size is affected by the gear you use and where you inject.
I can inject test propnate in my delts, calves with a 25g 1" needle and use a 23g 1.5 needle for t-400 in my glute.