I’m in search of a good solution to refreshing and repairing the brushed finish on my all stainless steel barbecue grill. A little research has taught me that the most common finish on SS kitchen appliances, is what is know in the biz as a “#4 Sanitary Brushed Finish”. The #4 designation comes from the depth of the scratches this finishing method produces and is considered to be shallow enough not to hold food particles and thus the Sanitary part of the name. This finish is used universally in both residential and commercial SS appliances. While a highly polished finish is also considered sanitary, most of us know what a royal pain it is to keep clean and looking good. Thus a brushed finish is much more forgiving in this area.
Now back to my solution search. There are several companies that make drum style sanding and polishing solutions specifically for this application, including but not limited to, Fein and 3M. These are fantastic options but rather costly. I’m in the process of rebuilding my SS grill, but I just need to remove a few scratches and rough spots. While I think a drill or other rotary tool is the best solution for a quick inline finish such as this, I just don’t want to spend $500-$1000 to do so. Any ideas from the metal working folks out there would be appreciated.
without seeing the repair areas - and just a guess on the finish appearace.
The first things that come to mind are brass wire brush on a drill or dremel if a small area. Drill for a larger area.
With a nod to using a SS wire wheel on a drill also. I would try to avoid using a base steel wire wheel since it can flake off iron and other flakes which can then color the stainless over time. Which is a pain.
SS parts often once finished goes though a passivation process that cleans the iron off the surface of the SS. Take 318SS for example (also called 10/18 SS by some) has a little bit of Iron in the alloy and if there are iron molecules on the surface they will rust and color. If you ever see a SS item that has brown dots and streaks on it - this is most likely why.
So a bare steel brush might well leave this behind too. Brass brushes might not be hard enough to get your desired finish style but I think it might. If not use a SS brush.
Hope this helps
Napalm is right, you shouldn’t use a steel brush on SS.
A highly polished finish can be hard to maintain, but a brushed finish isn’t much easier. The perfectly parallel lines will reveal the slightest nick, rub or scratch.
And it’s also difficult to match existing brushed finishes, both in coarseness and direction. If the appearance matters a lot, it might be best to plan on rebrushing the entire thing, top to bottom.
And I’d consider using something like a random orbit sander with a Scotch-brite pad or something similar. The random swirly pattern you get from an ROS might be easier to match in the future than the precisely linear pattern you get on commercial SS.
And if it’s just for yourself, I might just forget about it, and let it develop a “patina.” 
Most brushed finishes have a unidirectional “grain” if that makes any sense. Don’t use a rotary tool like a random orbit sander on these or you will instantly put very obvious circular marks on what is usually a straight-line finish.
Use a scotchbrite pad, the maroon ones are usually about the correct grit, and only move it in the same direction as the brushed finish. If you move it in a circular motion or across the grain you will instantly regret it. You likely won’t need power tools, a good new scotchbrite pad cuts fast.
Yes, but my suggestion was to use a rotary tool all over the entire grill, and get rid of the unidirectional brushed finish, because it’s hard to maintain.
Even with the correct grit, it’s hard to match the grain of a factory brushed finish. The slightest change in direction will be obvious.
A swirly finish all over will be easy to maintain. Any new brushing you do will blend in.
I’ve tried to maintain “swirly” finishes myself and I’ve always found them to be much more difficult to maintain compared to just using scotchbrite in a linear motion by hand. One of the major issues is working around protrusions like handles, thermometers, etc, I always got a very inconsistent finish doing that with a rotary tool and I also found it difficult to get close to the protrusion without hitting it with the abrasive too, wheras with a manual pad it’s easy to work it right up against a handle or gauge or whatever. It could just be me though, if the rotary method works for you then go for it.
Sure. Well to be honest, I’ve only done once or twice, and I removed all the hardware first, so there weren’t any protrusions like you mention.
I wonder if the easiest option is a satin finish (not a brushed finish) that has no visible scratches at all, but still isn’t polished to a shine. A lot of stainless steel develops that anyway, just through use.