I'm not planning to use manifold, just a small hose that they sell for small cans. You really don't even need a gauge if your cans add up to the proper amount, just charge till they empty. But i do agree that if you use Pag manifold/gauges then need to clean them first.
I used Robinair machine to recover and it sucked out 80ml of oil so i'll be putting same amount back.
Wow, i've never seen that. It must be a mistake on someone else's part from before...
My car definitely had a valve and nothing came out when i took both caps off.
I've seen cars not having High pressure port at all but never seen one not having shrader valve in the port...
Also, i don't think the cap is actually designed to keep so much pressure that high side creates (~300psi on a hot day i think?..)