I am creating a custom coin based on Forking Monero.
Once the build process has been completed, how do I go about actually mining the coin?
Is it possible to modify XMRIG to do this? https://github.com/xmrig/xmrig
Im going to assume you've setup a mining pool for your "custom coin", just set the correct algo perimeters on xmrig and point it to your mining pool. Nothing needs to be modified in XMRig