Just found this video in an older subcision thread. It does give you a rough idea on how subcision is performed.
A few remarks
1) There are large veins and important nerves in the face, and if you're not trained medically and don't know to look out for these, you could end up causing yourself a lot of damage in the worst case scenario. That's why I don't like the idea of anyone trying this on their own. Since dermarolling and needling use very short needles, they have much less risk.
2) I can't help but think that it would be so easy to accidentally punch the nokor needle through the skin and cause a big wound which would scar. I don't know how big a risk this is in practice.
3) It seems very hard/impossible to do this effectively on yourself in some areas, like the forehead.
4) You can see that subcision is performed in a surgical environment, using sterile gloves, a sterile needle, sterile everything. It is important to prevent infections, and one should be extremely careful about hygiene with any sort of home treatments, use sterile gloves, disinfect everything beforehand, use a sterile needle etc. And sterile does not mean wiping a needle quickly with disinfectant before getting started.