Me.
You write him just like me.
Okay here's the real protip:
Write backwards.
Start at the end, write in jumps to the begining, then fill in the gaps.
A good manipulator needs ro seem like he's in. Control of everything. Which means he's always on top of things. To do that, you have to cheat and know the ending ahead of time.
It also helps to be a manipulative bastard like me. Psychology is key. Know your tropes. People are unique snowflakes, but in large groups, they're just clumps of snow.
Everyone has their own song, but learn enough songs and you learn how people rhyme. If you want to get real good, get a job as a bill collector.
If you only get paid commission, starving is a great motivator to get gud.
You got 10 seconds to get inside someone's head or you don't get paid. Do that for a few months then work on a suicide prevention hotline. Now you got 10 seconds to get inside someone's head or someone DIES.
You'll learn how to manipulate damn fast.
Here's the key. Why? Why does he manipulate? For money? For greed or to eat? To save lives? Because he cares or because he needs to work off court mandated community service?
Manipulation does not mean two faced. It means leadership, comfort, usury, greed, desperation, and many more things.
Know the character first.