Im not familiar with the sweep picking but i can help you out with pinch harmonics. I was unable to do this for awhile but now i juss dont stop with em lol....i find it works better with heavier picks and dont give ur pick much room on the thumb when pullin these off. So ur thumb covers alot of the pick and juss the tip can be seen. But on the guitar you can find the sweet spot to hit the pinch harmonics...it works best in some parts of the fretboard....the best place to isolate and practise is on the G-strings 4th and 2nd frets....its easy to bend in this part of the fretboard and i guess u can later work pinch harmonics into scales when u get better with practise.

HOPE THIS HELPS lol
cheers