in the past I've had principals tell me to my face that they
cannot take my letter of intent/resume/whatever. They're not
allowed to. Other places here in Michigan have very strict
procedures for applying. Most places that I know of.
It's a good idea to sub in a district you're interested in.
That way, you will get around to different schools, experience
different grade levels, etc. And, it gives you a reason to be
in the building, and an opportunity to introduce yourself to
the principal and give a short spiel on yourself. That's
probably the best way for them to put a name with a face.
That, along with your stellar reputation for being a great sub
who is requested by many teachers!!!!!!