I did this on my Turncrafter. It's really simply - you just have to have a means to reverse the polarity of the supply to the motor. I did it with a DPDT switch in a box attached to the back of the tailstock with a magnet. You want to make sure that the switch as a center-off position, and adopt the practice of pausing for a couple of seconds in that position to make sure that the electrics settle down before actually switching polarity. One of the features of the Turncrafter is that the cable to the motor plugs into the control box using a standard Type C connector (commonly used for the power connection on desktop PCs) - so I just bought a Type C jumper cable from Amazon that had male and female connectors at the ends, cut it in half, and wired the reversing switch in the middle. As a result, all of the reversing stuff is either attached via magnets or truly 'plug and play', so I can restore the lathe to its original ex-factory state in about 30 seconds if need be.
I only use reversing for sanding, and then not on every project. It's probably more helpful on face grain projects (bowls, platters, etc) than on spindle projects. If you use it for turning, be aware reversing the direction of rotation can cause chucks to unscrew and that can be dangerous. There are a few chucks that come with grub screws that can be used to lock the threads to keep this from happening.
