The description in the rules says that during all battles players must show their entire hand of cards and then defender chooses their card first. Are the cards played in battle played face up? I'm assuming so, but just want to confirm...
Don't add rules beyond what the card says, play step 4 of the battle the same way by laying a card face down and simultaneously revealing. Just because you know what cards your opponent has doesn't mean you know which ones they'll play.