If you're going for this legit, the other guides here suggest doing this during the Wanted game mode. To be honest, you have to be doing well to get more than one pursuer and they will usually be all over the map, meaning the likelihood of two of them triggering a chase sequence is slim. I quite often escaped from one enemy, only to run into another to ruin my day.
I got this achievement in Manhunt, where for half the game you're guaranteed to have up to 4 pursuers on your tail. Blend in and watch your surroundings for enemies - other players will likely run to your location and then stop just as they appear in your view, so they'll still show a red arrow for a short period of time. Once you have two or more players engaged in a chase sequence, run away the best you can.
I found the smoke bomb and the sprint boost to be the best way of escaping. Don't attempt to smoke and stun your pursuers as quite often, you won't have enough time to stun them all, or one of them will be smart enough not to run into your smoke. Instead, use chase breakers and drop your smoke bombs in alleyways without chase breakers to slow your opponents down while you run around a corner and either blend or hide. Stay off the rooftops, it ultimately only slows you down. ‘Reset cooldowns’ is also useful to ensure that once activated, you’ve always got a fresh smoke bomb and sprint every time you respawn.
No doubt about it, this achievement requires a fair amount of luck to set up, so prepare yourself for quite a few near-misses before you get it right. Once particularly frustrating thing is your pursuers will often start to chase you but they don’t actually trigger a chase sequence. While it may seem tempting to rush at two or more of your opponents in the hope they will start a chase, quite often one will have a gun/knives/poison or a hidden ally will be around to knock you down. If you really must try to engineer it this way, run past them just as they’re killing one of your allies, as this limits the chances that they have abilities to spend on you.