If one has female pistachio trees coming into bearing age, can they be pollinated by grafting a male bud or scion onto a topworked female?
If so, assuming it's done early in grafting season and with more than one scion to improve the rate of survival, could it pollinate by the first season?
As it is possible (and normal) to graft scions onto rootstocks with a different genetic make-up, grafting male onto a female and vice-versa should cause no problems.
As for whether the male would flower in the first season, probably not. Pistachios flower on the previous season's wood, so you are unlikely to have sufficient flowering buds dormant on your scion to ensure proper pollination. It would also not be desirable, as you really want the scion to put on vegetative, not flowering growth in its first season so that it draws the sap more effectively thus maintaining the graft.
Long term you may find it difficult to maintain a tree with more than one cultivar present as there is invariably some discrepancy in vigour between the cultivars and one will usually die out. You also have to be able to remember which bit of the tree is which when pruning, which is not always easy!
