Can I apply an Apple Gift Card to my purchase if it's already been made on the Apple Credit Card?

I'm trying to buy a new refurbished laptop from the Apple Store. Insofar as I can tell, I cannot trade in my laptop and apply it to the refurbished purchase. I can still trade it in, but I get a gift card later on. So - I either have to wait to make the purchase until AFTER I trade in the laptop and get my gift card, or I need to find a way to apply the gift card to the purchase after the fact. And so that's the question: If I purchase a laptop using the Apple Card - or for that matter any credit card - can I apply the gift card I get for trading in a laptop to the purchase price later?

Or - do I need to trade in the laptop, wait for the card to be sent, and then apply it to the purchase price at the time of purchase (and risk the refurbished item I want not being available at that time)?