#1
I've been nailing pinch harmonics for a while but not as accurate it should be, I want to be able pop it off whenever I'm playing and when to use them to make it sound right :/.
I've been practicing them by trying to sound one off again and again.
How should I practice them to get it accurate?
#2
I practice by,
First finding the sweet spot for the note with your picking hand,
Then by playing up to and including the harmonic in your playing
This helps me get used to automatically finding the sweet spot, as it is different for every harmonic. You just have to keep playing the riff with the harmonic over and over again.
#3
I put my thumb almost all the way down to the bottom of the pick so my index and thumb are gripping it to the point where maybe 1 mm of pick is showing.

As you pick, if some of the skin on the thumb doesn't touch to bring out the sound, it's not going to happen right. You should know how to do natural harmonics.

Then I would pick maybe my lowest string (assume E cause 7 strings may not sound just right) until you hear that chorusy/flangey sound, this will usually indicate you are picking it properly. You might not hear it, IDK, I can hear it when I do it on my guitar.

From here then you just pick every fret until you get a good sounding one.

Use the bridge pickup.
#4
Just really pay attention to the angle of your pick the force you use and most importantly the amount of contact that is made with the string and your thumb after the pluck.
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#5
If you wanna get really good at them you gotta include them a lot in your playing and learn the spots for where you want to produce them. The spot obviously changes in relation to where you fret, you can test this by going chromatic down on the same string while PHing all the notes. That's why you can't learn the specific spots so easily and why PH a random note can be tricky. You can also form a barre chord and PH every string until you get the notes right, play the pentatonic scale all PHs etc. You'll start to intuitively know where they are. If you're playing a solo/riff with just a specific PH then find the correct spot for the note/pitch and practice it.
#6
I can't explain to you how to hold the pick as that is something different for everybody but it's hella important.

Practice the octave harmonics first.

If you play the third fret on E, pluck the string pluck the fret over the fifteenth fret on the E and play a pinch. Do that with all frets.

The octave is always on the half of the string length (i.e. half from the third fret in the specific case above ( physics mate, physics )).

The second important harmonic is always on the fourth of the string.

Then on the eight of the string length.

There are some " less " important ones.

If you get have a strat style guitar, pinch it always on the left or right side of the pickup - it's usually where the harmonics are for some reason.