I have drawn/injected with the same needle and sometimes it's ok, on the larger needles sometimes it makes like a "barb" and will hook some skin when I remove the needle so I always switch tips.

There is no hard and fast rule, you can draw and inject with a 27 gauge if your patient enough (I've done it) or 18 gauge if your manly and think scars are cool.

When I'm on a blast I do my HCG sub q, when I'm on my TRT cruise I mix it, allows it to flow though a smaller gauge needle with very little effort (I also will cut it with B12 sometimes).

Oh yea, virgin muscle, you will get PIP, in time it will lessen.

I recommend shooting your quad, you don't want to be dependent on ANYONE for your TRT