M, that will manually control the speed (position) but automatic slow motion of the servo such as in gear retract from "open to closed or visa versa" requires the movement from 1 to 2 milliseconds (or whatever range required) be done in small increments.
For example, first send 1.0 then 1.05 then 1.1 etc etc.
Possible with discrete devices but just the ducks nuts for a small uC........(AND plenty of code and examples out there at Arduino or Picaxe)
For "how a servo works" also plenty of info online.