Pecs are easy as pie...one of the very easiest shots you can do.
My favorite rotation is; delts, tris, traps, pecs.
For all of my injections, I use a 25g 5/8" pin. A 25g 1" will work perfectly. I just hit alot less veins with a 5/8", but I end up with some lumps because the oil is not deep enough under the muscle to keep from being an obvious lump.
For pecs, I draw an "L" inward from the nip. I go two inches in (toward the center of my chest), and two inches up. I then angle the pin downward just a hair...maybe 20-30*.
I suggest never using more than 1cc in a new muscle. Start out with .5 if you can. Work up to 1 cc. Then work up to whatever is comfortable. I have injected 2.2ml in each pec in the same day before. the most volume I have done is 2.2ml. I use frequent injections to avoid lots of volume and lessen the sides from gear.
For me...I have never shot glutes...don't want to. Hard time reaching around there anyway. Quads..did them forever. Then it seemed like quads started to be even more of a bitch than biceps. They hurt more and for longer...I hit more veins and nerves than anywhere else. So I dropped them completely.