Currently booked through UA, HNL-NRT operated by ANA, UA flight #, UA R class.
Is this correct in order to request PP upgrade for ANA flight?

1) Find out what the upfare is to eligible Premium Economy fare class (what is ANA's minimum fare class for PE to J?). If price reasonable, do it.
2) Call UA and ask to swap in NH native flight number
3) Use link in post #384 above to request upgrade
4) Cross fingers