My thoughts on what an old finish look like are based on handling the old firearms. Each one is a bit different but within each category there are many similarities. For revolvers I have seen some that are almost totally devoid of finish but most of the ones I have dealt with have some of the finish left. Faded, but still present. Usually in protected areas like between the rammer and the barrel, or where the recoil shields meet the frame, or the sides of the hammer, or for revolvers with flutes cylinders, in the flutes.
When I go for an aged look, I try to imitate that and therefore do not strip the finish but remove it with care and leave some where it would have been found on an actual old firearm.
Think about how the finish is removed from an old firearm. Some is by contact with corrosives but much of it is by friction. Being carried in a holster and the constant rubbing of the leather on the metal polishes the finish off the metal. But only in places where the leather contacts the metal. Cylinder fronts were rarely touched by the leather but were in contact with the black powder residue which removes the finish in a different way. Sights were constant polished by the act of drawing the revolver and also shortened by the friction though it would take a lot of that action to shorten them enough to visibly see it. (Unless a silver or gold coin was used as a replacement. Then they would have a flattened top edge from being filed to sight it in {maybe} but certainly flettened from the work of the leather on the coin.)
Grips usually took the brunt of the damage. Just being exposed while the rest of the revolver was covered in leather allowed the weather to work on the varnish and age it. Same with things like tables, stirrups, ropes and just a well callused hand.
On the metal, I use a green dish pad, synthetic steel wool, and rub area where the leather would have rubbed. For the grips, I usually wear a rough old glove and handle the wood until it shows where I need to remove the finish and than use the green scratchy pad to accelerate the process. A very light application of acid in spots can sometimes etch the metal but should be used sparingly. Sometimes I will remove wood from where it mates with the frame to simulate shrinkage, not much, just a sliver.
Plated revolvers get a differnet treatment as they age differently than blued ones.
If this sounds like a bit of work, you're correct. But I don't care for the totally bare metal look. And I have not found a shortcut that gives me the look I like. Most of the easy methods remove all the finish with little or no control about leaving anything behind.
This is one I have started and you can see some of the barrel finish has been removed as well as the high points on the cylinder.

This photo shows a more fully aged revolver with a new one. You can see where I left the finish in the protected areas.

In this photo, the top revolver was stripped partially and then has been carreid and used for about 30 years. You can see how different it looks from the bottom revovler that was only stripped maybe 5 years ago.

To get a aged look, you need to proceed slowly. Much of the aging is a subtle process and I have not yet figured out how to speed it up. WIth very few exceptions, chains or beating with rods and such does not add anything.
Good luck.