Oatmeal Stout... with raisins?

I just brewed an oatmeal stout yesterday.. this is my 3rd brew ever I'd like to stray away from the norm a bit on this one.
OG: 1.075 I also used 4 ounces of Belgian Special B.. which imparts a raisin/prune flavor.
I would like to add raisins to my secondary... but I have a few questions.
1. What kind of raisins should I use and how much?
2. How much additional fermentation should I expect if any?
I want this beer to taste like an oatmeal cookie that gets you drunk.
Please only answer if you have experience with this, speculation isn't going to help me.

you will likely get wine flavors with it. Raisins are generally used to make certain strange types of wines. If you want a cookie flavor you may want to add some lactose to keep some sweetness to it. Don't know what you'd want for type. You will want to chop them before tossing them in though.

Another idea would be to add some chopped and partially rehydrated raisins to the glass after you pour as is sometimes done with blueberry beers.