I know as a newbie, the needle size was a major issue with me. I had read to use a 22G pin. My first box of pins were BD brand 23G (Precision Glide 305145). I had a mental block about using a 22G seeing as it was larger diameter. The gear I was using was oil based and very thick.
To make a long story short this size pin was very difficult to use because the inner diameter was simply too small. I went through a major process of preheating the gear in hot water etc to get it thin enough to pass through the 23G pin. Then doing more research on pin sizes I purchased Nipro brand 23G pins (AH-2325).
All Nipro pins are thin-walled. Here is a chart the industry uses for wall thickness etc.
In a nutshell the Nipro 23G thin-wall has 1.7 times more inner cross sectional area than the BD 23G I was using previously. In fact the Nipro 23G thin-wall has 1.2 times more inner cross sectional area than even a standard 22G.
Bottom line is, I found a huge difference is ease of use by using a thin-wall 23G as opposed to a standard wall BD 23G.