Do a test piece first,
1. fluxing with water thinned out white paste solder, (very thin).
2. Sprinkle gold dust/filings on.
3. heat from the back first to have the dust/filings bond to the solder (that way the flame from the torch doesn't blow them off)
4. come back in for the front with a soft flame and get the metals to sweat. At some point you should see a texture in the silver rise a bit & see the bond form between it and the gold.
5. Quench, clean & re-flux & do the process again, this time you'll be able to use a bit more heat.
6.You'll also able to planish the surface at this point if you want it smoothable.
Please, This is just one approach, let others kick in and see what other methods come up.
All this depends on the shape and weight of the piece you're doing, Extreme thick to thin areas will be really tough.