Well it depends on how much you want to use but honestly I pin sub q the majority of the time but when I do IM, yes I'll do both bi's. I stuck to pecs, delts, bi's, tri's, calf's, You can pin anywhere you want but lr3 will go systemic. If you want spot growth you can micro dose it meaning split that 15mcg into 3 5mcg injects into each muscle.
You can pin post wo if you want. I did and had good results but supposed to blunt natural mgf(mechano growth factor) production. Then I did pre workout. Great pumps and overall worked just as well. I also did first thing in morning and that worked well so my guess is as long as you use it, it will work.