Modern sail winches are proportional, they position themselves according to the position of the controlling stick. This is why most yotties prefer to use a ratchet stick for the sail control. Saves wear and tear on the left thumb.
If the rotary knob that Ashley mentioned is a proportional channel, it will do the job OK.
Using a single line usually means having an elastic line tensioner to ensure that the unwinding drum does not leave a pile of slack line which will tie itself round anything available. Unshrouded drums wrap the line under the drum, shrouded ones find other things to tie the line to.