We always play "after." Ditto for the ones providing a reroll, or the one-time-use shields that completely negate the damage from a "miss."
Or in other words, we assume (and allow) that the discard-to-use cards can be used before or after or basically any time you choose. Obviously the "discard to use a fire/water/earth/wind elemental die" from the expansions need to be used before you throw. But Voodoo Doll or Cloak of Invisibility would be much worse if you had to use them before throwing as insurance only (or intentional miss, in the case of Voodoo Doll).
This is correct. You can use discard-to-use items any time you want.