How to Get Rid of Bathtub Stains

So, I have tried recommendations online on how to clean bathtub stains and none of them seemed to work real well and if you have the plastic type tub, it seems to turn black easily. I recently used Soft Scrub with Bleach to clean our bathtub and it worked really well. I squeezed a bunch of it on the tub and let it rest for a couple of hours. To help spread it around, use a dry sponge. After waiting a couple of hours, I then scrubbed the tub and rinsed it out with water. After I scrubbed the tub, the tub was noticeably a lot whiter.  Sorry, I do not have before and after pictures, but Soft Scrub is not that expensive so I recommend trying it.