So let us say we have a cool but rude on the battlefield, and it is level 2 so whenever you attack you can discard a card. If you do you then draw a card.
Now with that setup you're attacking with an Ironshield Elf. The Ironshield elf is able to discard a card to become indestructible until the end of turn. Since you have diclared you are attacking, and cool but rude triggers are you then able to use Ironshield elfs ability while attacking to discard another card. Since cool but rude says Whenever you attack you may discard a card. If you do draw a card. So Ironshield elf would discard a card, cool but rude would draw (?), cool but rude would do 2 damage to the opponent, and then you could start the cycle again with the card drawn from cool but rude?