>>56052100PKHeX if you can dump the savefile, comes up with the option to just set EVs manually and skip the boring grind.
If you can't doomp, the depends on the game. Read about how the EV items work, especially the vitamin caps so you can know when you have 100 EV in a stat so you can deduce IV in older games. In newer games you have a graph in the info screen and no vitamin caps.
