This may not be 100% correct but I believe that in order to play a card from the shared resource you must first switch out a card from your hand ( I believe that also counts for the first phase of your turn - i.e. Draw/discard)
Actually, the cards from the shared resource are considered cards from your hand when it’s your turn, so you don’t have to do anything special to use (play or discard) one of them.
the only time you would be "replenishing" the shared resource would be the result of a nightmare card
When you use one of the cards of the shared resource, you must replace it by drawing the top card from the deck –so you actually replenish the shared resource each time you play or discard one of its cards.
you must first switch out a card from your hand ( I believe that also counts for the first phase of your turn - i.e. Draw/discard)
Here’s the thing: if you have in your personal resource a card that would be useful to your partner, you can make sure he/she gets it by transferring this card from your personal resource to the shared resource. In order to do that, you have to discard a card (any card) from your hand (personal resource or shared resource), and then you may swap the card your partner needs with one that is already in the shared resource. All this counts as the first phase of your turn, so you must now replenish your hand (in this case, replace the card you discarded in order to do the swap).