Divination actually isn't inherently about speaking to the spirits. Divination is the practice of seeking knowledge of the future or the unknown through supernatural means. Astrology, for example, is a type of divination, it involves the stars, not the dead. Some people ask the dead about the future -- but I wouldn't recommend it, because they're unreliable compared to other sources. Because people are unreliable, they hold grudges, and quite frankly they don't owe you answers. Using tools which are for divination for communication purposes, while possible is also often a bad idea. Unless we're talking about something like pendulums. But they don't allow for conversations.
Using something like Tarot cards to communicate with the dead is, frankly, quite unwise considering how open and malleable the meaning of the cards are. They mean something different to just about anyone who reads them. A good reader is really more like a therapist than a medium because they are drawing out the solutions from the person seeking them. Not the dead.
Mere moments ago you were asking me how one communicates with the dead, and now you're suddenly an expert? An expert who thinks that the possession by an unknown spirit -- one which might be violent, as demonstrated by the fact the house is cursed and Carstairs was recently found murdered in several different ways -- is the best way forward? The safest way to communicate with the dead when we know that they could be potentially dangerous is the way we've successfully managed it so far: a seance.
But all means - try to let the entities that have cursed this house possess you. I won't stand in their way.