Doing this will probably get you any pokemon you want but it requires a master ball and a extremly strong pokemon

first get a pokemon holding a master ball and level between 90-100

then you can but it up for trades and wait for it

choose your pokemon but make sure for the pokemon you want has to be hacked for it

once you've done this wait for you pokemon to arrive i got a Mew level 30 for a empoleon level 93 holding a masterball

and after 3 days the mew was level 65

why do it this way because searching trading with a cheated pokemon cant be traded so get someone else to go through the hard work finding you the pokemon while you sit back and chill