AC system maintenance / repair / recharge

Excellent, detailed post, Lech.

@Mendel Leisk: leaving it up to the pros would be great, but I think true professionals like @lech auto air conditionin are extremely rare. If I had a guy like Lech that was local, I'd just bring it to him and pay up. But I don't and nobody has more interest in maintaining my car than me. I think there is a greater risk leaving this job to the local "pros" than learning how to properly do it myself.

Moving on to the next step: I ended up purchasing a Testo 550i Digital Manifold Gauge kit.

The seller sent me a manifold that is "nearly new" instead of new/unused. I don't want to contaminate my hybrid system with incompatible oils (PAG etc.), so I want to clean the manifold before using it on my Prius. Am I correct that even trace amounts of incompatible oil in the manifold is a legitimate concern, or am I going overboard?

I watched @lech auto air conditionin video on how to clean a manifold gauge:

I do have 99% alcohol on hand, but I don't have nitrogen. Can I blow out the manifold with compressed air and then pull a vacuum to remove any moisture, or is the nitrogen essential for cleaning the manifold?