It is really not difficult and the method can be used for bending wood in general.

My people were boatbuilders and shipwrights when they weren't farming, and I grew up bending wood. 

The only hard part is reading the grain of figured wood so you don't crack the stock on 10 grand worth of Perazzi. 

Straight-grained stocks are pretty well… well… straightforward.

Build a serious, full-length jig with common heat lamps. The Big-Box stores carry the lamps cheap.  This jig is two layers of ½” CDX sheathing laminated together using construction adhesive.  Carved, contoured, carriage-bolted oak blocks at both muzzle and action padded by soft cedar shims make for zero slippage of the gun, which is required to protect the bluing.

  Just don’t bend the tubes by overtorquing those nuts.  Trigger guards always come off for bending. With the guard off, double check to insure the wrist doesn’t have any repairs. 

Polyurethane and resorcinol glues are the only ones that’ll withstand heat.  All the others will let go at well below 180 degrees F… including epoxy, PVA, casein, urea formaldehyde and hide glue.

To protect the finish, the wrist is wrapped tightly with several layers of cheesecloth and tied with string.  Don’t leave any air pockets or the finish will bubble on you.  A meat thermometer poked into one of the triggerguard screw holes measures temperature, a pocket watch keeps time, and a teakettle is used to heat peanut oil to just shy of boiling – around 200 degrees F. Peanut oil has a high flash point and doesn’t smoke, whereas linseed oil smokes and burns too easily.

The jig needs a brace to pull the stock into, and an index to measure how far.  Fancy is a plastic grid.  Simple is a couple of string lines riding in notches (which are easily moved with a dovetail saw and square when required) and a set of dividers and a rule.

Heat the wrist, keeping the cheesecloth soaked with hot peanut oil.  After 20 full minutes at 180-190 degrees, try to bend the stock.  Keep heating until it bends easily, some wrists are thicker than others and some wood denser than others.  It’s the heat that plasticizes the wood’s cell walls, and it has to reach all the way to the core. 

For applying pressure, fancy is threaded rod inset into captured nuts let into the brace.  Some even saw apart C-clamps to use the components.  Simple are padded clamps.  Note the C-clamp I’m using as an anchor has a scrap of leather glued to it as a pad.  Be liberal with the peanut oil… keeping the varnish wet is the only think keeping it from bubbling.  Also note there is a hole in the jig base to recover the oil using a pan beneath the bench.

(The reason I use a double layer of CDX for the base is for stiff… so I can cantilever the jig onto my workbench using clamps, so as to have the excess oil free-fall into a pan on the floor rather than run all over the bench top.)