i'm not here to say practice but hopefully soemthing useful.
When you are doing palm muting, that position is actually very good for a pinch harmonic.. but again.. if you are doing it wrongly, lt'll just go haywire. Try a few of the following methods.
1) Make sure when you do a pinch harmonics, you are holding the pick close to the tip.
2) Make sure your palm is cleared off the required string but not way high. Pinch harmonics requires very little string vibration thus the clearance isnt that much.
3) If you can get a faint harmonic sound, check on the gain of your drive. Certain pedals only allow the sound to come thru at a certain gain level, normally higher = better. If you've the sahasrara pedal, you need not tweak your gain up to get the pinch out clearly.This way, you'll maintain a nice overdrive sound and yet get the harmonics out clearly.
4)Which pickup are you using when doing this? This is the same when you do on a classic guitar. The more you move your right hand towards the bridge, the easier to get the harmonics. So in this case, you should be using your bridge pickup.
5)Good setup on your guitar also helps alot on doing this kinda thing! A poorly set up guitar will often result in people losing their patience and feel like a lousy guitarist! "if i give a tgm to steve vai, i believe he can play it like his jem evo!" I don't agree to this line at all. To play well, you need a proper instrument. "If i give a proper guitar to steve vai, i believe he can play like his jem evo!" This should be the correct idea..
Hope it helps dude! just my 2cents!
Gr3y