There are many ways to cut a rabbet with planes: moving fillister, plow/chisel, fenced rabbet, etc.
I choose using only a rabbet plane for most of the moldings I cut for a few reasons. It's an easy plane to set up. There are no depth stops and no fences. It's the single plane you'll use for adding all rabbets and chamfers that we've already seen. When you use a fillister or plow you'll need another plane (probably a rabbet) to add the these features. It's not a big deal for a woodworker with a wide variety of planes to do that. It is a big deal for somebody starting with none of these options.
An unfenced rabbet is ideal for what we'll be discussing. It's the difference between one plane and two (take note that the other two are significantly more expensive and have many more parts, which means more things that may have gone wrong over the last 100-200 years).
How does one go about cutting such a rabbet? There are many ways to do this too: auxiliary fences, battens, etc. Here's an option that I've helped scores of people nail on their very first try.
The luxury of this process is that when it comes to cutting the 2nd or 5th rabbet there's nothing to adjust. You only need to mark the rabbet.