Do you need help for your keys?
The most robust and customizable way to achieve true auto strumming on the native Guitar Hero 3 PC port is by using , a free scripting language for Windows. This method intercepts your fret inputs and instantly fires a strum input at the exact same millisecond. Step-by-Step AHK Setup
Download and install the latest stable release from GitHub.
If you prefer to play with a keyboard but want to reduce the need for independent strumming, external macro programs offer a workable solution.