Are these finishes actually finishes intended for firearms or are you talking about something a hobbyist or someone else applied in place of actually getting a gun properly refinished?
I thought we were talking about actual gun finishes and not simply any imaginable type of finish that someone could potentially apply to a gun.
I knew when this started that it would come to this. Use of words like "hobbyist" and "properly" and "any imaginable" show a deep seated bias against thinking "out of the box".
A Gunsmith is just what it says, Gun Smith. A Gunsmith is a "smithy" that works on, creates, manufacturers, guns for his/her clients (if properly licensed). You can be a "gunsmith for the museums", or a "gunsmith for the people", or both. A gun can be either a museum piece or it can be a tool, or BOTH!
A gunsmith must decide from questioning his client whether the gun will hang in a humidity controlled case or will be used by a craftsman as a tool.
If the client brings in an original 1851 Navy revolver for restoration to original and has the money to do the job, bluing, a highly toxic and labour intensive process, is indicated, if needed.
If the client brings in a unique, original, octagon barrelled, muzzle loader that he wants and has the money to restore, then browning, less toxic, but still labour intensive, may be indicated.
The hours needed to produce these finishes will be expensive to the client...unless the gunsmith just loves doing the work and doesn't charge what he/she is worth.
On the other hand, if a LEO brings in a Saiga 12 (AK-47 in 12 gauge) that he keeps bouncing around in the trunk of his squad car along with a tire iron or two, its a tool that needs to work when asked to and needs to be rugged enough to be used as a tool. A beautiful bluing job is counter-indicated. It wont last a week in the trunk. A good hard coated paint job is what he needs.
Or a rancher wants an AK-47 built so he can kill wild pigs that are ruining his cattle's watering holes, a gun that can get 6 to 8 pigs before they scatter, he doesn't want a fancy blue job. He may want a camo paint job. Bluing doesn't come in camo.
There are a couple of very good paints, Duracoat, Ceracoat, and probably others that are epoxy based. Some are petrochemical resistant. But as with bluing and browning, the high end paints are labour intensive and expensive compounds. Not necessarily suited to the trunk of a car or hunting pigs.
Then for the guy that walks in with a Stevens 820B (worth $150 at the top end) or a $450 AR15. There are the "other" paints.
The Stevens took 20 minutes to strip down, 30 minutes to sand down the flat black engine paint the previous owner had applied and subsequently ruined with a transmission fluid soaked rag, and 20 minutes with an air brush and deep green Rustoleum to make "pretty". After repairing two springs and adding a new bead sight, he had $150 invested in a home defence gun that still looked good. He was happy with his tool. The Rustoleum can be repaired in minutes with an air brush if it does become chipped.
I am gunsmith to several law enforcement officers and also to ranchers. I am a gunsmith to the people. But if asked I can create a museum piece, if you have the money for it. My speciality is custom AK-47s in any calibre you want....within reason LOL.
Most of my clients don't have the money for a museum piece in the bed of their pick up or the back of their squad car. They want a tool that works and doesn't rust.