What can I use to get black marks from the toilet due to plunging?

Try Comet and a toilet brush.

https://www.hunker.com/13420973/how-to-remove-toilet-plunger-rubber-marks-from-toilet-bowls

Bar Keepers Friend?

Pumice stone is available in the toilet brush area of your grocery store or hardware store. It doesn't damage the porcelain and does the trick .

Maybe try a pumice stone...I've heard people talk about it but have never done it... Good luck.

Have you tried a pumice stone? They will take just about anything off toilet bowls.

I would try a pumice stone, available at Home Depot or Wal-Mart. Second thought, I have seen recommendations to use WD-40 on toilet rings and stains, but you probably need to use something like a non-scratch scrubber along with it. I also love Shawspads that have removed stains, after trying a multitude of other methods. Link to their site, but you can also purchase through Amazon (at a higher price)

https://smile.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=Shawspads. I bought the 2 pads for $4.99, and can't remember what Shaws charged to send... http://www.shawspads.com/category_v3.aspx?categoryID=23

Have you tried the Mr. Clean scrubbing pads?

Try an a small emery block. The type you use for smoothing your feet.

Black marks in a toilet can be caused by a number of things, including the use of a plunger. To remove these marks, you can try the following:

1. Use a toilet bowl cleaner: Many toilet bowl cleaners contain powerful chemicals that can help to remove stains and marks from the inside of the toilet. Simply follow the instructions on the cleaner to apply it to the affected areas.
2. Use a pumice stone: A pumice stone is a natural abrasive that can be used to scrub away stains and marks from the inside of the toilet. Wet the pumice stone and use it to gently scrub the affected areas, rinsing the stone frequently.
3. Use baking soda and vinegar: Mix equal parts of baking soda and vinegar in a small bowl to create a paste. Apply the paste to the affected areas and let it sit for a few minutes before scrubbing with a toilet brush. Rinse the paste away with water.
4. Use a commercial toilet stain remover: There are many products on the market specifically designed to remove stains and marks from the inside of a toilet. Follow the instructions on the product to apply it to the affected areas.

I hope this helps!

A pumice stone on a wand much easier to use since you don't have to bend down nearly as far.