I used raisins in a Tomme Arthur dubbed recipe but I didn't realize that I should purée it and add it to the fermenter....so I had to stir like crazy for the last ten minutes of the boil, after I added the raisins to the late boil. But it all turned out fine and the dubbel was later bottled and waxed for long term storage. It has held up well!
But if doing it all over again, I would add the raisins to a small pot with a bit of water in it and bring it to a boil and purée after, then add to the fermenter at high krausen or a touch later.
As noted by the others, Special B can get you very close taste wise, too, though slightly different in flavor.