Polish Brass

After polishing the surface you might want to preserve it from tarnishing with a clear coat...

Unfortunately in my experience the clear coating is not really airtight and the brass underneath will tarnish which leaves you with a worse end result requiring the stripping of the clear coat before you can polish it again.

Remember the Japanese motorbikes where the lower Quality Aluminium casting when polished was sprayed with clear coat, great on the showroom floor but out in the real weather disaster.

That's probably because the surface was not properly prepped, or the clear coat was scratched or something....If done properly, the clear coat is moisture and air tight...

https://www.practicalmachinist.com/vb/general/clear-coat-brass-237196/

I used to play the Sousaphone in the band.

I used a lot of that stuff!

, then

What is the thing on the left?

I tried just the Brasso, and I guess I have to do all the super fine sanding first. it got to the bright brass color but still a satiny finish no mirrorlike.

The Brasso will remove the oxide but the micro-pits may require some elbow grease. Maybe a buffing wheel on an electric drill might polish it off...

Glassfibre brush. Used by traditional draughtspeople and model-makers, among others.

You could try T-Cut first, then Brasso. It works for me.

Never heard of T Cut, but did do the multiple grades of sanding then a polishing wheel, came out not too bad,

Elbow grease used with progressively finer abrasive paper up to 600 grit, followed with rouge with a cloth buffing wheel.

I always use Brasso to polish brass and use a lambswool buff on a sander with speed control to buff the brass back to mirror finish and finish off with a clean buff. Depending on the size of the tube and the surface finish it may need to be sanded with wet and dry paper starting with 600 grit and going to 1000, 2000 and 5000. You can use jewelers rouge and a power buff if you really want to get a superb finish after the wet and dry and have the hours to spend.

Brass is soft and will sand/buff easily. I agree with the Brasso. However, the brass will soon tarnish and any clear coat will detract from the mirror finish. Perhaps this is why the old-time engineers who took care of equipment always carried a polishing rag with them and used it on a routine basis.

Back in my navy days, we used the heck out of this...