Make sure whatever software you're using you "do not pass" the movement keys (WASD). I'm guessing you already wrote a macro on your slave,

/tar Main
/follow

Or I think you can just do /follow main, I'm not at home ATM. What's probably happening if you're telling him to follow, then you hit your forward key, he'll automatically stop following since the "W" is getting passed to both windows. Not sure if that's your problem, but it's definitely a start.

Welcome to the club!