Look at my pics, I have some in which I selfsuck. It takes some warming up though.
The key is to bend the back : for me it's legs over head, feet agasint the wall. And I push with my feet to get my midriff closer to my mouth. Obviously, it helps that I'm 7'4, but I've seen pics or vids of smaller guys doing it better than me (there is also that my cockhead is quite big and I have trouble taking it all the way into my mouth in this position).
If I could bend a bit more, my torso would not hinder my jaw when I open my mouth, and I could get more of it inside
Compared with the regular way of jacking off ? I'd say it's different. I selfsuck when I'm in the mood for it. It feels reaaaaly good. I'm not too vocal when I jerk off, but when I selfsuck I can't help moaning around my cock