Authorizing CFIs for a club

I'm looking for issues involved with a private flying club allowing CFIs
to instruct in its planes.

If the club just contracts with an FBO to provide instruction, than I
suppose this is a moot point, as the FBO takes responsibility. But what
if a club member CFI wants to provide instruction? What procedure
should the club use to approve a person to provide primary instruction
in its planes? Just saying "show me your current as a CFI and that you
have insurance" doesn't seem like enough. The FAA has supposedly
already authorized the CFI to instruct, but just being a CFI doesn't
make one a good, or even safe, instructor.

What is the liability of the clubs' board when they allow a CFI to
provide primary instruction in its planes?

Please let me know what has worked for you in cases like this.

Thank you!