'Not sure if this is what you're after. These will do what you seek; up to and including logging any commands entered into the switch afterward (recorded in the day's Administration report of ACS 😞
set tacacs server {addr.} primary
set tacacs server {addr. of secondary}
set tacacs key {secr. key}
set authentication login tacacs enable telnet primary
set authentication login local enable telnet
set authentication enable local enable telnet
set accounting commands enable all stop-only tacacs+
