So site rotation isn't okay on the first cycle? Because he should only hit one site, every time?
Or, he could go ahead and learn new sites, and prevent scar tissue buildup by rotating sites, regardless of what he chooses to use, and how often he has to inject, accordingly.
Even if it is every day injections, he could easily have more than enough EASY sites to hit.
Both ventrogluteals, both triceps, both delts, both quads... 8 sites. All easy to hit. And all can be learned in a 30 minutes on google.
Also, while post injection pain is pretty normal on the first few injections of anything, none of it should be crippling. If your prop is causing significant pain, I suggest you find a new source for your prop. No reason it shouldn't be painless, or at the very least, almost painless.