Oh it's not slowly at all.
With my Tragus, it was very fast, the whole procedure was over with in under 20 seconds, including getting a tiny ball onto the tiny ring. I now can get the damn thing off so it was put on well.
My nose was slightly different. The needle it bent and it was done by a different peircer. He talked to me about kids and silly things they get stuck up their nose and then the excuses they use throughout (After explaining the procedure) the actual needle took less than a second. The stud took a while on my nose because it is a circular curved back and it has to be at the right angle.
A needle peircing will heal much faster and is less likely to give you problems afterwards. A gun will cause more scarring and doesn't allow room for swelling enough. also the studs aren't hollow and so it's pushes the skin out of the way. BME goes into more detail.
But I have had both gun and needle...All my gun peircings have played up, the first set I had to take out as my ear was so swollen the backs of the earrings were getting a bit lost. And other sets I have started to get a reaction to the metal and so have had to change them after a few days (NOT recommended).
I am still yet to change any of the studs and rings in needle peirced holes, I just don't see the need to change them because I like the ones I have now and there are no problems with them.