Depending on how tough the stains are, you could use a pumice stone if really bad. I've dropped denture tablets in mine to help with the cleaning and cutting down on the scrubbing. We have 4 so I usually hit them each once a week. Rather than a toilet brush, I like a swab. It does so much better of a job and you can push the water out of the bowl for a good clean on the sides as well.
I use a steam cleaner. It gets it clean without harsh chemicals and the temperature of the steam sanitizes the toilet.
I use Dow toilet bowl cleaner with bleach once a week. It sparkles.
I put in a few squirts of Dawn dish liquid in the toilet. Pour in a few cups of vinegar (by eye) into the toilet. Use a toilet bush to foam it up and leave it for an hour or two. Then a little scrubbing with the toilet brush. The suds suspend the vinegar above the water line.
Place 1/4 cup 20 Mule Team Borax sprinkled in the bowl. Brush bowl with your toilet brush, then let sit for 30 minutes. Flush