I currently have a fairly manual process when releasing a new build in TestFlight:
Have you seen the nomad CLI tools for iOS development? They let you do things like:
Manage Devices
$ ios devices:add "iPad 1"=abc123
$ ios devices:add "iPad 2"=def456 "iPad 3"=ghi789 ...
Manage Provisioning Profiles
$ ios profiles:list
+----------------------------------+--------------+---------+
| Profile | App ID | Status |
+----------------------------------+--------------+---------+
| iOS Team Provisioning Profile: * | ABCDEFG123.* | Valid |
+----------------------------------+--------------+---------+
Build & Distribute through TestFlight
$ cd /path/to/iOS Project/
$ ipa build
$ ipa distribute
And more!
All examples taken from the nomad documentation.