I need a tool...

We have extremely hard water. Enough iron to leave rust stains on the side of the house if you aren't careful aiming the lawn sprinkler. Even with a water softener there is significant build up on the shower stall walls and the bath tub. It's a regular job to scrub this stuff off. Last time I used those green #M scrubbing pads. My knees and shoulders don't take well to the effort it takes, so I need a tool. The little shower scrubber power tools won't touch this job. 

I have thought about using my buffer and some liquid rubbing compound. Anyone have a better idea?

Needle scaler and an air hammer. At like 20 psi...

You need the right cleaner. For me, it's between KABOOM! and Super Iron Out sprays for the bathroom where a sponge will remove the stains after a short soak.

WildScotsRacingCampbellCougarSeed said:

Needle scaler and an air hammer. At like 20 psi...

Start with cleaning the shower, and end with a full bathroom renovation?

In reply to sobe_death :

Super IronOut has little impact on this stuff, unfortunately.

Cordless drill and scrubby 3M pad on a chuck.  HF sells a variety of them.  

or maybe a random orbital sander but with 3m pad?

Fix the problem first. Contact a water treatment outfit; the water softener is obviously not enough.

Before we got our acid neutralizer our dishwasher would get brown and we would run the washer through a cycle with Tang (the powered drink mix) instead of soap and it cleaned it back to white. You could maybe try that but as RossD suggested a proper system will clean whatever is in the water out before hand. Our issue was manganese (sp) and it was eating the pipes from the inside out.

Vinegar. Distilled white vinegar. This can be diluted 50-50 with water and sprayed directly on the stains. Let it sit for a few minutes to loosen the stain and then hit it with your 3M pads. 

There's a couple of whole house iron filters out there for like 400ish dollars that work in tandem with softeners.

Other than that I use uncut CLR when build up gets bad.