You will not find any specific documentation about applications and GTM/DNS.
The main reason is the fact that GTM does not process the application traffic, it just gives an IP in response to a question about a FQDN.
If the application you want to load balance with GTM is Cisco AnyConnect or Microsoft Exchange, it will be the same from GTM point of view.
However, there are things you need to think about, and those are the same for every application.
Like, GTM persistence and GTM monitoring.
For persistence, you need to decide if the user should continue to be sent to the same data center or it can go to another data center.
For monitoring, how you check that the Cisco AnyConnect is up an running, as the GTM has to be aware of the status of the application?