I do both. I find that home compressors and especially the plug-into-the-lighter compressors do not have the required CFM to get it all out. I start by blowing out the system, then I isolate and drain the water heater, then I flush the water heater using a hose and wand while I pump pink stuff into the house water. Then I blow out the system again. Remember to get the outside shower lines. By this time the water heater is well flushed so I let that drain and insert the plug loosely. I put a yellow sticky over my water heater switch that says "Water Heater Bypassed".
