If you know the metallurgy of what you trying to join, you should be able to work out from the INFO - last thread- what filler to use. Other than that seek assistance fro your supplier.
If I can teach High school boys to silver solder ,I can show anyone.
It is an easy to follow a procedure.
I'll assume you have an oxy acetylene plant .If so set it up on 2 to 3 psi regulator pressure. Use a nuetral flame on minimum setting. As a guide you should be able to wobble the flame.That setting is very important. Low pressure,low volume is the go. Flame settings that are too high will cuase the solder to prematurely oxidise.

Also is the cleanliness - sanded up to shiny clean. your flux if dried out can be brought back by adding water until it regains a cream like consistency. Place the flux only where you want the solder to run.

Heat the larger of the two components to begin with as it will take longer to heat and gradually allow heat to transfer to the lighter part.This is important as both parts need to be the same temperature if the solder is to flow and run correctly.
Do not introduce the solder until the temperature is suitable. An indicator of that is from the flux colours.It will go from a dried toothpaste appearance on initial heating to a clear water like appearance until just before before the correct fusion temperature. A quick rub of the filler wire against the desired fill area will be rewarded by the wire taking immediately between the fusion faces.

Remember that the parent material temperature is what fuses the filler rod.It should not be melted with the flame.

The solder deposit should finally appear a shiny golden colour.If it looks dull or grainy , it has been overheated .

a bit of practice won't hurt

Grahame