I have a Sar Arms B6P compact that is developing some rust issues after almost 2 years of carry.  The slide stop has some small spots but the mag catch gets so bad if I don't pull it out on a weekly it gets stuck.  I would love to send it out and have it refinished but I can't justify $150+ into a gun that cost me less than $300 in the first place, so I'm hoping there is something I can do at home that will work on these small parts?  I've done Duracoat plenty of times but it seems like paint would make the part too thick, or at least if I put it on thick enough not to just rub off right away.  Also tried cold blue and keeping it well oiled but it rusted just as fast.

KG Gunkote. Spray thin and bake on.

Today's most durable "paint type" gun finish is Cerakote.
It's tough enough that some gun makers are using it as a primary finish.

Preparation and application is absolutely critical, much more than the other paint type finishes.
Failure to closely follow the directions results in a substandard finish that won't stand up.
You'll hear home finishers complain that Cerakote isn't durable or looks bad.  This is invariably cause by not following the specific instructions.  There are no short cuts.
Their web site has a tutorial that shows the details.
This includes the exact type of media to use to bead blast, baking to drive out oils, and application spraying.
Cerakote is one of the thinnest finishes.

You could probably get the gun processed by a factory authorized service cheaper then plating or bluing.

https://www.cerakoteguncoatings.com/

https://www.cerakoteguncoatings.com/resources/files/training/Cerakote_ELITE_H-Series_Training_Manual_WEB_1-17-17.pdf

Brownell's sell Cerakote in both air curing and oven curing.

Other do it yourself gun finishes are parkerizing, and slow rust bluing.
Parkerizing is rather easily done on a stove top with minimal equipment.
You can get zinc phosphate and modern mil-spec Manganese phosphate from Brownell's and they sell a pre-dip that makes standard parkerizing come out flat black.
Brownell's also have directions and you can find directions online on Youtube.
Also, Brownell's have how-to videos on the pages where the two types are listed.
Brownell's sell standard zinc Phosphate parkerizing in pints manganese in gallons, and these are available from several other sources.

Slow rust bluing is also fairly easy, but it's somewhat messy and takes several days.
Unlike the paint type and parkerizing finishes, slow rust does not require the parts be bead blasted.
The finish is a satin blue color that's actually more durable then modern hot salts bluing.

NOTE: on Cerakote and other paint type finishes the TYPE of bead blasting media is critical.  Use the wrong type and the finish will not adhere.  Read the Cerakote site for what type to use.

Before you go and refinish parts, try cleaning and applying Eezox. I used it on an 870 that would surface rust just from a humid day. I was astounded at how long it's lasting.

Thoroughly degreasing parts.

Warming them.

Immerse then in Break free CLP while warm and allow to cool.
Wipe gently with a cotton rag.

Use.

Norrell's moly resin is still a great finish and a lot easier to work with than Cerakote.  It wears almost as well and is somewhat self lubricating.  Apply with a $10 Harbor Freight airbrush and bake in your oven or a $5 toaster oven from Goodwill.

Cerakote is something I still do a lot of, but it doesn't dry until you bake it so you have to do a lot of prep to spray and bake without touching the parts.  It's also comparatively expensive.

I use Duracoat also.  Just use reducer to make the coat thinner.  You only need to spray enough to color it. That won't make it very thick.

Do not try parkerizing on your home stove if you want to remain married.    Do it outside or at least in a well ventilated area where the steam won't get on anything that can rust.  I do it outside on a Coleman stove.  But yeah, it's pretty easy if you follow the directions (if I can do it must be).  Besides prep, keep the temp constant and do not let it boil.

You are welcome to send the parts to me. I’ll rust blue them no charge.

I read about people using high temp header paint with ceramic so I gave it a try. I did a RIA revolver that was a project anyway so I had nothing to lose. Disassembled, sprayed, and baked in my Traeger at 325 for about an hour.......... I'm shocked at how well it's holding up. Plus I had just cooked bacon, so the gun smelled like bacon for about a month!

I used the ceramic header paint (flat black) on a FAL several years ago.  It had close to 1,000 rounds put through it with practice, an Appleseed and one field shoot before my youngest son got the itch for an M1A.  Darn thing looked like the day we put it back together from the stripping/prepping/painting project.

I've told myself, for years, I was going to do it again, to a different gun (had an 11-87 that looked pretty bad) but just never got around to it.