This is mainly for guns carried IWB. Some parts of the metal will be in contact with your skin and could potentially rust. So, what's the best finish for a CCW?
I’ve been reading a lot about this. It seems that Glocks used to be pretty rust resistant. But since they have abandoned (only for US guns?) the Tenifer finish (I know technically it’s not a finish, but let’s not get into semantics) they are not as good as they used to be. I’m reading that Walther is using Tenifer tough. The Nitron finish on Sigs seems to be pretty good too. Other guns have a stainless slide (like Kahr) and I’m reading you can buff out any minor rust.

Then there are some other considerations as well. For instance, you can have a nice finish on the slide, but the metal mag release will rust (for CCW, plastic mag release is better then?)

I have about 3 Glock pistols I have carried IWB almost daily for YEARS. The finish they have on them has held up very well. One pistol was carried in a Kydex holster, which puts a lot of rubbing on the finish. It has some wear marks, but nothing major. I am a huge Glock fan, and like their pistols a lot.

A good CeraKote will also hold up well, if you want a custom color.

Rustoleum

I've carried my stainless Kel Tec a bunch and never had any rust. Not even very many wear marks honestly.

Are those Glocks the older version (brighter more slippery finish) or newer (mat and non slippery) version?
I have both. I haven't carried them that much, but the older (shiny) version seems to be more scratch resistant.

Gen 2 and Gen 3 Glocks mainly. I have 2- G29's, one is a Gen 4. I have a G40 in 10mm, which is Gen 4. I can't tell the difference on the finish. I am one of the few who use my pistol as a tool, not a collection piece or work or art. I use my tools, but don's abuse them. If they get a scratch or something, I think of it as a character mark.

Duty Coat (Dan Wesson)