When you’re ready to make big changes, definitely look into threading as an alternative to waxing, a lot of folk find it less painful in the long term. (But it still really stings at first! :) )
Having thick/full eyebrows can be an advantage, since you have more to work with. I have the problem that my upper eyebrows are a bit too sparse, which makes them much more difficult to shape.
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!