I have called coyotes and foxes with just them. If you see a coyote out in a field and can get within a couple of hundred yards, just use the squeaker. It is amazing how far they can hear it if it is calm.
When calling tight areas I will sometimes start with the coaxer for a few minutes before I go to the big calls.
I like them for foxes more than any other call in cover.
You can also sometimes bring in a held up coyote when you switch to a coaxer. It is weird, they will often come at a run toward a coaxer even after they get suspicious.