If you met a blank slate of a person, they weren't that good at talking, didn't do much, basically no personality, What advice would you give them to change that ?

No advice, being blank is ok, live and let live

They are excellent against psykers!

Fun hat?

Go out more

You can't change people. They are who they are. If it doesn't work, move on.

Find something you're interested in. (For me, Star Trek) Find a group that is also interested in that. (For me, sublistnooks about that) Engage in it and see where it takes you. When you're passionate about something and are with others who you know are also, it gives you something to talk about and confidence to do it with. Then you can just see how it develops and how your conversation skills and everything goes from there. 

I might try to find ways to influence them. See if I can make them like me maybe lol.

Do much and you'll get better at talking