I use oxygen and propane for my brazing. I did not want the expense and extra safety concerns of storing and using acetylene, and in particular did not want to get involved in contracts given the small number of frames I am likely to build as a hobbyist. Though contract free acetylene cylinders have become available, personally I see no advantage in using acetylene for building lugged frames, but it does have advantages for fillet brazing. Propane is relatively cheap and long lasting and widely available for a small cylinder deposit. I use a 11kg cylinder. Smaller ones are OK but I have found the larger cylinder more stable, especially when using a gas fluxer, I don’t know why. Storing the smallest size cylinders of practical use of any flammable gas is common sense.