Once again forgive me for the quality of my response I'm on the road till Monday.
I discussed in another question why I feel using drones to defend is a legitimate strategy. And I discussed how you need to use your drones to counter a rush. So I'm guessing you're looking for specific micro-ing techniques for using drones, and not a discussion for stopping rushes, as that's kind of been discussed to death.
Using Drones is a lot like using Zerglings they're both Melee units (a rare commodity in SC2), so they both rely on surrounding your opponent for victory. This means the standard sorts of rules: Don't engage near buildings, Move to surround before attacking, Don't focus fire, etc.
So let's focus on the Drone specific techniques:
- Attack Ground, not units (A then left click the ground). If you tell Drones to attack ground (instead of specific units) then they won't laze around after killing their target
- F1 will select any idle workers if you are microing. CtrlF1 will select all idle workers so you can Attack Ground again.
- Box all your units and add them to a control group. This will make it easier for you to send them all back to work when the battle is done.
- Micro the stragglers. Because Drones are Melee, it is possible that not all will be able to attack at a given time. If some are caught behind others, micro them around behind to help your surround (or back to work).