The answer is: cardtext!
If the card indicates "ready vampire", then it doesn't work. Otherwise, it works with vampires in torpor (= that are not ready).
(That's why it's important to include cardtext in your question).
Prince of Paris, France
Ratings Coordinator, Rules Director
As LSJ would say: "cardtext".
Name: Blood Doll
Cardtype: Master
Master.
Put this card on a vampire you control. During his or her master phase, this vampire's controller may move 1 blood from this vampire to his or her pool or from his or her pool to this vampire.
Name: The Rack
Cardtype: Master
Master: unique location.
When this card is played or the controller of this card changes, the controller chooses a ready vampire he or she controls. During the controller's untap phase, the chosen vampire gains 2 blood. A vampire controlled by another Methuselah can steal this location for his or her controller as a action.
More explicitely: a Blood Doll can be used to move blood from/to a vampire in torpor. The Rack will give blood to a vampire in torpor.