I do both, air first from the city water connection, around 80 pounds of pressure for several minutes. I then close all the faucets and apply pink under pressure from a bilge pump mounted in a 5 gallon bucket. I then proceed to open the faucets one at time. Every one of them, 3 sinks, 2 toilets and the shower spit out clear water for about a second before turning pink. Is it enough to harm anything? I don’t know, but I sure sleep better during our long cold winters.
To answer Hogan’s question when I am done with the above I disconnect the line before the pump and stick it in a gallon of pink and repeat the above.
To each their own and whatever works for them.
Niles