I totally forgot what i used, but i had to switch mid way through my cycle. I ended up using a guage that took like a solid 2 minutes to suck up a mL cuz it was too small, but when i injected, it left no mark and i couldnt even feel it. I never bothered with switching the needle to draw and then a new one to inject. I think it might have been a 25 i was using. it was difficult to inject cuz there was so much backpressure trying to push such thick oil through a tiny hole.
just curious, when u pull the needle out, does some of the oil ever come back out? i had that problem. id leave it in there for a min after. duno whats the best way, but it worked most of the time.