A half-cab is the same move as the switch (see the link to the switch at the bottom of the page), except you're doing it from the switch-stance position - that is, the foot which is normally in front is your back foot because of the wake 180 switch you just did. A half-cab is actually easier than a wake 180 switch because your body automatically wants to return to its natural stance.
For the half-cab, pull out even less than you did for the wake 180. You will pop surprisingly well on a half-cab because you will have a slight forward lean going into the wake. When you ride in your normal stance, you naturally favor your back leg.
This translates to good news when you are switch-stance. You will still favor that same leg, but this time that leg will be in front - thereby giving you the better pop. Do your half-cab just like you did the backside wake 180 and you'll be looking like a veteran rider.