Quick Question on adding yeast for bottle conditioning

So I've got an Imperial Stout that has been conditioning/aging for 6 months (the last month it's been sitting at 42 degrees or so) now, and I'm thinking I'll need to add a touch of yeast at this point at bottling. I think I've seen people mention a half pack of dry yeast should suffice, but my concern is that the yeast will lower the gravity too aggressively. Final gravity is 1.022, and I know the alcohol present will probably curb too much yeast activity, but just wanted some input.

P.S. - I also know that I could probably take sample and add a bit of sugar to see if there still are viable yeast, but I'd rather skip that step, if possible.

Anything?

I'm sure that there is plenty of yeast in suspension, even at 42 degrees, to carbonate the beer.
I've heard of people adding a half pack of dry yeast at bottling time, but you shouldn't have to. I don't think it would really hurt anything.

Hope this helps.
Cheers