By "be able to see the TLS+SRTP" I assume you mean "be able to see the decrypted TLS" ?
The guide you outlined is actually the one I followed when I googled for this topic. However, I can't get it to work. The list of different certificates on CUCM is long and I'm not sure which certificate to pick. When I go into my Cisco phone's Security settings (CTL FILE) I see that CAPF server is defined as 'CAPF-01b24746' and I was able to find a certificate with the same name in the CUCM certificate list, so that's the one I picked....but again...it doesn't work!
See attached screenshots. What am I doing wrong? As you'll notice the Wireshark version (1.12.8) I'm using has a different UI for the SSL settings and the SSL logfile states: