Adding yeast before I bottle (how much?)

So this is really a two part question. I have a Belgian Strong Ale currently around 10%ABV this is sitting in a secondary fermentor. It has been in secondary for about 2 weeks and I plant to keep it there for about 2 more months. Some of that time will be at lagering temperatures. I plan to add yeast back in when I bottle condition (about 2-6 months in corked belgian bottles), but I have no idea how much to add. Or what sugar source to use: DME, Candi, table sugar, corn sugar...

The second question I have is that in anticipation of adding yeast for bottling I saved some of the yeast from primary. I basically used the yeast washing technique, but I didn't have more than one jar so what I have is really just a whole lot of yeast and trub. It's a smaller sized Ball jar filled about 65% with solid packed yeast and a layer of beer on top of that, there seems to be two different layers within the jar, a darker layer on top of a lighter layer. It's been in the fridge like this for about 2 weeks, and I was just wondering if I can in anyway still use this as the yeast I add when I bottle condition. Part of me doesn't want to risk it since I will have so much time and money already invested into this beer. But if I was going to use this yeast how much would I add and how would I go about cleaning it up at this point?
Thanks

I'd get a fresh pack of the same yeast strain, get maybe a 500mL starter going with it, and pitch at peak activity along with your priming sugar. And cross your fingers.

How to Brew has a good how-to for priming with yeast for lagers (or beers that undergo a long secondary).