www.silversupplies.com/catalog/metals/silver_solder/paste.shtml

Kitchen vinegar is going to be the solvent that you use to remove the parkerizing from the barrel and FS thread.  Just don't allow the vinegar to sit where you don't want to remove the parkerizing.

Once both threads have been stripped down to bare metal, take a dremel and slot down the barrel thread on the top and the bottom.  This will allow the Silver solder a place to thicken up more than just threads to threads.

Now apply Silver solder to the threads, index the FS, then coat the barrel just below the thread line with insulating paste. The insulating paste will keep the heat from transferring down the barrel, and keep the silver solder from wicking down the barrel as well.

At this point, light up the FS with the Mapp torch until the FS becomes a dull red (Not bright red, and the past will start to flow before the FS is dull red, but you need the FS that dull red color to make sure that the barrel underneath has gotten hot enough to allow the solder to bond to it as well.

Once you entire FS is dull red, remove the heat and allow the FS to cool.  
Once the FS has cooled down, hit the FS with Cold bluing (cold black).  This will recolor the FS to the Black to match the parkerizing on the barrel.  
From there, wash off the insulating paste and to neutralize the cold bluing, then lube the parts with CLP to give them a protective coating to the parts to prevent rusting.

Lately, I have been questioning the legality of silver-solder attached muzzle devices.
From my interpretation of the laws, if you can "remove the device with common hand tools", it would not be considered to be "permanently attached"

I have had a few barrels through recently with silver soldered muzzle devices.
I wrap a piece of leather around the front sight base, clamp it in the vise and a 6" long 3/4" wrench has been able to pop all of them off.

Those "hand tools" are about as "common" as you can get...

I suggest the "pin and weld" method instead.



If you do use a torch and solder the muzzle brake, be very careful when you re-finish the whole thing that you don't leave the parkerizing solution under the threads.
A good penetrating oil is recommended so you don't end up with this:

Quoted: can any type of welder be used?   or what would be best my buddy has a mig welder would that work?

A tig welder and a qualified operator is best.
I'm no good with a tig and don't own one so I use a mig and they come out fine.
The most important part is in the removing and cleanup of the excess weld and then the re-finishing.

Quoted: What kind of grinder (dermal?) do you use to clean up the weld?   Where is a good place to get the stuff to make it black?

I use a Boyar Schultz surface grinder with a Suburban 5C collet master spin indexing fixture on a magnetic chuck.
That's probably a little higher tech than how anyone else does it, but I get really good results so it's well worth the $2000 worth of tooling I use for the job.



Touchup bluing makes it black when you are done grinding.
Any good gunstore has it as does Brownells or Midway.