When I used prop quad and glute shots screwed up my ability to walk normal, so I just shot the stuff in my bis, tris and delts. I later did this with tren, but did not see the same results as with prop (tren was alot less painful though). The swelling from the prop must have helped stretch out the fascia or something.
For tris I had 2 injection points. The first was at the top of the horseshoe for the short head. To do this keep the target arm at your side and reach across, shooting straight in and towards the body (there was a video on AF of some guy doing it this way). This can be tricky if you have a big chest... I'd have to stretch out before I did the shot.
The other is in the long head of the tricep. Put the target arm over your head as if you are doing an ab pose, and you will see a pronounced notch in the tricep long head where the lat tendon inserts (roughly 1/3 to 1/2 way up the tri). I would shoot at the top of this notch, angling the pin upwards a little.
For both I used a 25g 1"
I tried the 5/8 pins but liked the 1" alot better because the pin stays still by itself (which is important when trying to aspirate with one hand).
I saw a slight reduction in top-end tricep strength (under 5 reps), but I think it might have been a mental thing (fear of muscle tearing or something).