There isn't a method that's as easy as Reset bag to display the number of EVs on all stats then Soft Reset in X/Y/OR/AS. However you can use Isle Evelup in Poke Pelago to EV train if you want a specific EV spread. At rank 3, Isle Evelup gives 4 EVs per session of training. So if you wanted something like 176 Speed EVs on a Porygon-Z, you could set it to train on Isle Evelup with a speed increasing drink for (176/4=)44 Sessions. It's time consuming, but you can do something else, while it trains, and it doesn't require power items or Pokerus to be as efficient.
(E: forgot to mention the fact that if you press Y on the summary screen, the hexagon of the stats will switch to the hexagon that represents the EV spread, similar to the one on the super training screen in X/Y/OR/AS, and the name of the stat will sparkle if the EV for that stat is 252. But I think you already knew that, I'm only mentioning this in case.)