Pinch Harmonics can be a very frustrating thing to learn. I found them hard to teach for a long time but I think I have it down now. Pretty much all my students can do it fine after watching this video - so check it out and hope you get them too!
Make sure you check out TE-501 • How Harmonics Work too so you understand what is going on.
The video should explain them better than text... I hope ;)