I'm curious how these modern takes on One Piece will deal with the Okama and related characters (assuming they get that far!)
I haven't read the manga, but the anime at least comes off super-transphobic in how they're played for laughs at times. I think that'd necessarily be cut from the live action version, but less hopeful about this for another anime adaptation.
There's definitely just some variance in terms of how much it bleeds and whether it hurts. I haven't really noticed any pattern in terms of injection site; I think there are a lot of factors. Holding the vial and maybe rolling it between your hands can help warm up the liquid, which makes it a little bit easier to both draw and inject.
The needle size will affect these things too -- the thinner the injection needle the less blood I've seen, but then it takes a little longer to inject. Do you know what gauge you're using to inject with?
I found the whole process very stressful for the first several weeks, but eventually it just became routine!