The key element in blood magick is blood, not self-injury. Sterile lancets are great if you just need a pin-prick. If you need more then I recommend sterile needles or small gauge piercing needles (~20 Ga). The goal is to start the bleeding, get as much as you need, then stop the bleeding. Also… you may be doing this while in an altered state, so you’ve gotta get you shit together and know what you’re doing.
I also practice sex magick and have a penis. So my favorite technique is to prick the head of my cock when I’m erect. The blood flows easily and stops easily with simple pressure.
Stay safe.