It is really funny your new "team member" is called indeni 🙂
For the matter, yes you can script it with clish. Use set user password-hash instead of the password. Take hash from a known password, or generate with md5.
If it was not Indeni, I would actually recommend Radius user defined, but here you do need a local user.
For remote execution, I would recommend using cprid utility, ran on your MGMT server CLI:
$CPDIR/bin/cprid_util -server <IP_address_of_Security_Gateway> -verbose rexec -rcmd /bin/clish -s -c '<your single clish command'
This allows you to avoid admin authentication before you start dropping commands.
Send each new CLISH line with a separate command. Do not forget to use 'set config-lock on override' for the first one and then 'save config' for the last, on each GW.
Test your script before mass deployment 🙂