Unfortunately, in my opinion the only way to do Craigslist hiring is in gang interviews - you set aside a few hours and bring a bunch of them on site. It's not great, as it feels discourteous to the decent guys, but there are so many posers/phonies/just plain desperate guys out there that you can't afford to set up proper interviews. On a first-come, first-served basis, give them a couple of 2x4s, a bag of mixed nails, pencil, speed square, a hammer, and a chop saw, with a drawing showing a mini-wall with plates and some studs, with specific measurements - plate needs to be 36 5/8", for example. Studs are 24 9/16", or whatever.
Tell them they have 5 minutes, and it's OK if they don't finish it, you just want to see how they go about it. Set a timer, so you're not standing around waiting. At the end of the day you have a list of guys who have some sort of a clue; now you can start figuring out how to filter out the druggies and violent offenders.