Where you pinch makes a difference, and you dont have to pinch to hard or totally reposition the pick to get them.
If you've already got them, just keep practising them. How long have you been trying to do them, cause usually when people start out they have troubles like yours. Just keep at em and you'll get them great.
And they also tend to come through nicer on a pedal than just on your amp set to distortion, like yours. If you can try out or buy a good distortion pedal, then I recommend you do so.