Hi Andy,
AVT is one recommended method for recording prompts;
•Administration Via Telephone
Administration Via Telephone (AVT), previously known as the Greeting Management System (GMS).Administrators also use the AVT to record and manage Cisco Unity Express automated attendant prompts and alternate greetings for the automated attendant.
Recording an Auto-Attendant Greeting or Prompt File
Two methods are available to create auto-attendant greeting and prompt files:
•Create a.wav file with the following format: G.711 u-law, 8 kHz, 8 bit, Mono. The file cannot be larger than 1 MB (about 2 minutes). After recording the greeting, use the GUI or Cisco Unity Express CLI ccn copy url command to copy the file in to the Cisco Unity Express system. See the next section, "Uploading the Auto-Attendant Greeting or Prompt File," for the upload procedure.
•Use the AvT on the TUI to record the greeting or prompt. Dial the AvT telephone number and select the option to record a greeting. When finished recording, save the file. AvT automatically saves the file in Cisco Unity Express.
The AvT prompt filename has the format UserPrompt_DateTime.wav, for example: UserPrompt_11152003144055.wav. You may want to use CLI commands or GUI options to rename the file with a meaningful name.
Cisco recommends using the AvT on the TUI to record greetings and prompts because the AvT provides higher sound quality compared to .wav files recorded using other methods.
From this doc;
http://www.cisco.com/en/US/docs/voice_ip_comm/unity_exp/rel3_0/administration/guide/voicemail/5AAttnd.html#wp1011691
AVT & Triggers;
http://www.cisco.com/en/US/docs/voice_ip_comm/unity_exp/rel3_0/administration/guide/voicemail/4AvT.html
http://www.cisco.com/en/US/docs/voice_ip_comm/unity_exp/rel3_0/administration/guide/voicemail/1syscmp.html#wp1013372
Hope this helps!
Rob
