in Splunk answers you can find many scripts to install forwarders, these are some examples:
On Linux it's doable. We create a standard unix id for all these servers and via python or ansible deploy the Universal forwarders to them in bulk.
The thing is that there is a set of prerequisites which we need on the servers, prior to the installation, such as connectivity to the splunk servers, dedicated file system, write access to the file system, read access to the logs. All of this we also did via a python script.