I know of no proper DIY 'flush'. A proper Ester Oil flush requires specialised equipment to be performed correctly... nitrogen or chemically dried air. If you can all components are to be flushed.
Flushing with anything else, including refrigerant is unproductive.
More normally you simply drain the oil then pull a vacuum on the entire AC system for 30 minutes then let it sit under vacuum (hold) for a further 30. Done.

You can run the 134a compressor with 12 or 12a no problem. Where do you get 12?

Drain the oil from the replacement compressor. Install it. Pull the vacuum as above... if it maintains vacuum through the 'hold' part recharge with refrigerant and away you go. If it drops below 27 inches of mercury (27" Hg) find the leak before charging.

__________________
I don't know the same things that you don't know.

Shayne

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