Is it possible to silver braze steel parts printed by a 3D printer?
I think because bronze is added into the part matrix, it will be more braze/solder-able than stainless steel alone.  It should also lower the temp solder needed to get a good bond.

The trick will be to get the part hot enough to flow the solder without deforming the sintered matrix

I would use the slightly hotter MAPP gas (over propane) for the lower temp silvers.  If you need the harder silver, you may have to step up to acetylene-air. here's a typical light brazing setup (minus the gas bottle, of course.  That's a local ).  After that, propane-oxygen and then Acetylene-ox

There are a range of silver solders with different melting termeratures.  In general, the higher temps are stronger.  The fluxes are matched to the solder.  There are silvers with the flux bonded to the outside.

Silver solder pastes (several pastes) with the flux mixed in are nice to "reflow" solder with.  You assembly the joint with a minimum of paste, heat until it reflows(melts).

Stick and wire solder involves fluxing the parts, heating until the flux flows and the (usually water) liquid boils off.  Solder is immediatiatly added  with heat applied until the solder flows and wicks around the parts.  Immediately remove heat and let cool without disturbing the joint.  Applying the solder too soon will result in a lumpy "cold" joint with little strength.  Practice on scrap first.  

Cleaning of the joint is usually done with mildly acidic sulfpheric solution or pickling solution

Eye Goggles, gloves, ventilation (flux smoke) and a small bottle of co2 fire extinguisher would be advisable. 

None of the product references constitute an endorsement, they are listed to show a "typical".