Carl wants to start up a podcast running four different XLR mics through a mixer. He wants multiple channels for each one. Is the mixer what he needs? Leo says that while condenser mics are more accurate and hear everything, he really wants a coiled diaphragm mic, which doesn't pick up everything - just the voice. Leo uses a Heil PR-40. But for a budget, the Shure SM58 mic is very forgiving. Leo says for a mixer, the Behringer XR18 is great. He can control it from an iPad, it has great mic pre-amps, and is simply a good choice.
Since the instructor is currently using a handheld mic, a better solution would be a wireless lavalier mic. The challenge here is that a lavalier mic picks up more ambient noise and there is a higher potential for feedback with the PA system. It will be important to make sure there's enough distance between the mic and the speakers to avoid this. A lot of companies make lavaliers, but here's a few to choose from: