How to delete dispatcher cache without logging into Dispatcher server

Download and install the latest ACS Commons library version via /crx/packmgr/index.jsp. It can be downloaded from here.

Go to  http://aemhost:port/miscadmin and copy the out-of-the-box Dispatcher Flush agent as many times as needed and modify (set with the IP of each dispatcher).
For example:

dispatcher1

General => Enabled
Transport => http://10.43.32.126/dispatcher/invalidate.cache
Triggers => Check these boxes: Ignore Default, No Status Update, No Versioning
 
dispatcher2
General => Enabled
Transport => http://10.43.32.146/dispatcher/invalidate.cache
Triggers => Check these boxes: Ignore Default, No Status Update, No Versioning

Configure Dispatcher Flush UI to delete everything in the cache under */etc.*in the cache folder. Refer to the documentation.