Glad to help. :wink:

All you will need is:

2x Relay 6v coil and double position contact (make sure you get the right relay to handle your motor in terms of amperage)
2x Diode (regular diode that can handle 1/2a is enough)
1x Servo circuit board



This works very well, i use this circuit to control my drive motors and will use to control my DIY linear actuator, but i never tested it in battle becouse i am from Portugal. Using an ESC like Plargen sugested is the best/most comon way to control a linear actuator.