Hi. its quite easy. Just buy a pair of lightweight "push and hold, to make switches". Then glue them directly to a minI servo, spaced so that the servo arm is just touching each.
Then, servo operated one way pushes one switch to on and it operates the winch until you release when it automatically switches off. Connect the motor with polarity reversed to the other switch so that operating the servo the other way causes the winch to run in the opposite direction until released when it stops again
Cost of bits - about A£5-A£8 from EBay.