Do not use those what you call "ports" to blow air through the system. Those "ports" are test cocks, for a Cross Connection Device Inspector to test and certify the device. You will damage the device and it will no longer protect against backflow if you keep blowing air through it like that. I have seen many damaged RPZ's where a home owner thought they could save a few bucks and do exactly like you posted.
Below is a picture of what you are talking about, they are ¼ turn ball valve that are installed in the device to test the unit. There should be a total of 4 of them on an RPZ assembly.