Servo's have there own PID controllers. You can google the term but i will give you the info you need to know.
Basically, the are two values the servo cares about.
1. where it is now
2. where it is told to be
the further away these two values are from each-other, the faster the servo will move. (up to a certain speed).
So for what you are asking, if you wanted a servo to move more slowly, only tell it to be little off what it is now. Think of it as a carrot in front of a horse. The further away you hold the carrot, the faster it will go to try to get it.
So here is some psedu-code that should help.
while (position < goal)
position = position + 2;
You play with the value added to position every time (in my example, 2) and with how long the delay is to change how fast the servo will move.
To synchronize the servos like you ask, i would add an IF to the loop that checks if the first servo has gotten to a certian poition, then sends the second servo it's new position.
Hope this helps, and you understand servos a little more.