I can tell you as someone who just passed the exam last week there is no one silver bullet for the exam. I will say I'm fortunate my organization paid for the self-paced training, but wasn't not enough. CGRC is heavily focused on NIST and a bit of ISO standards. You will need those documents and they will be of great resource for sure.
Take the outline and begin to read domain by domain and look for information wherever you can find them online to supplement. I study a lot with AI, by asking for deep clarification of concepts, compare with different models to reduce the possibilities of hallucination.
Despite having CISSP for over a decade close to 2, the exam got me so bad, I wasn't sure until I was giving my report sheet.
Don't overthink it set your goals- it took me like 6 months to be fully ready with steady study.
All the best.
