The polish looks good, but like Stophel I fear rounding. This said sometimes photos are shockingly revealing and sometimes shockingly deceptive. "Square corners" in carving scrolls etc that are not.
But just the same I will blunder on here and give some advice anyway.
If you are not using a hard backer on the paper you will round things. Somethings can be polished with the paper held in the fingers or folded and rolled tight etc. But a hard backing is far better for any place it can be used for the less experienced.
I seldom file an entire lock casting before trying backed 150 grit or even 220 wet or dry.
I will use a file to clean up problems I know won't clean with paper and the file used right WILL maintain shapes well. But then you have to polish out the file marks.
For backing I use either 1/4" plexiglas cut the to length and width I want or a couple of "T" aluminum extrusions about 8" long a friend gave me.
Use double stick carpet tape to stick the paper. The thinnest stuff you can get. I like to make the plexiglas just narrower than the tape and the paper just wider than the tape. Keeps adhesive off the work. The aluminum extrusions are just about tape width, 2"
This is MUCH better than wrapping a file with the paper. Files tend to cut through.
I use round files, dowels and pieces of heater hose, fuel line ect as backing as well depending on the shape.
It is better to do edges and any contoured surfaces first then do the large flat areas. This is usually best for keeping edges sharp. Do not "bend" the plexi glass by applying pressure at the ends while polishing. Keep it flat.
Round parts such as round barrels and rod pipes etc. Can be polished with wet or dry backed with duct tape and the paper then used in a shoe shine type fashion. NOTE this WILL round things and remove decorative features ect from parts but on round parts rounding is not a problem so long as you don't work down the ends of pipes etc.
Unless you intend to have the parts color casehardened I would not go to 600 grit. Instead used 0000 steel wool and chrome polish this will remove the scratches and make a uniform finish.
If you intend the brown the part 320 is fine enough 400 or 600 will actually make it harder to brown/rust blue the part.
This looks pretty good. Decent edges and no "whoop-de-doos". Doing the the large flat surface last in every grit with hard backed paper will reestablish the edges that define the bevel etc.
Dan