Lead with this.
You're an artist and in theater or film creativity is the currency of operation. Add some personality. The first one is a quick follow-up letter after a first encounter. Remind the talent agent where and how your paths crossed. Awesome, awesome, awesome. I still think sending by P.
Do not try to make something sound better than it is. Close Strong Refer them to your headshot and any other enclosed materials. Go in for the kill.