1. It can have varying amounts of pain depending on how much you actually suspend yourself. Since only 11 pounds is needed to sufficiently compress the carotid artery, if you reach that threshold, then it's not too painful. The main problem with partial hanging is that SI (survival instincts) are really hard to fight with this method, because you can just simply stand up. Speaking from my attempts I recommend sitting on a chair, pulling the rope taut to a bit higher than you can reach, then fastening it. That way you are sufficiently dangling while also grasping to the chair in the bottom.
2. I know what you mean by not finding the carotid arteries. I had so much trouble trying to find them during my first few attempts. My advice is, when you feel a faint pulse on either side of your neck, grasp those points really hard, push inwards, then upwards. Don't be fooled: CTB is always an uncomfortable process and there's no such thing as a completely stress-free choke. Some days I can find them, some days I can't. I agree with the previous person about putting socks or cloth on either side of the ligature (small wet face towels I find to be best), to better help compress them. However if you're in you're attempt then as a last resort you could always block your jugular vein or windpipe instead.
I hope you achieve whatever you wish for.
