It did work? The guide provided above is for Testnet only; if you apply the guide above in Mainnet, I don't think it would work. Usually you need to run a mining pool because it requires a stratum protocol if you want to mine solo.
Just in case if you want to try running your own pool, you can try any of these below
You are correct. After getting everything set up, I was getting the GBT error when connecting to the BTC Core. I'm currently mining to ck pool. Thanks for the info! I'll look into the pool software.