What you could try is, get 2 pokemon that know memento (i.e. 2 muks) and let them lead in a doubles battle vs an NPC, make them use memento on eachother, whichever one is alive after the other uses memento will fail since the pokemon that shouldve been there died to its own use of the move, then bring in your sketch smeargle, making sure its faster than your still alive memento pokemon, then have it sketch it on turn 2. in theory it should work.