1. If you just got the doll, they loosen up quite a lot during the first weeks if you keep bending her every day. I’ve had my new stiff jointed doll for less than a week and she’s already feeling like her joints are loosening up. I just hope she doesn’t become too floppy as I quite seem to like stiff joints and positioning her. Another loose-jointed doll I’ve had up until now feels so limited because pretty much all she can do is lie down.
2. Do no harm to your doll. Be patient and you will find that they gradually loosen over time.
3. You just need to use her joints every day for a while, do not force them to move, you can break her if you force it too much. Just have to be careful and slowly work them. If your doll is silicone then I wouldn’t be injecting her with any form of oil. Mineral-based or synthetic oils will degrade/destroy silicone, which just leaves plant or water-based oils.