There's not a really good way I know of to figure out pitching rates for bottle conditioning. For a 5 gallon batch 1/2 pack of rehydrated dry yeast should be plenty.
I think it is a waste to use liquid yeast for bottle conditioning. The flavor contribution will be minimal at best. That said, I have use wine yeast for my belgian bottle conditioned beers and I thought the results were very interesting.
finally, unless you have a high gravity beer or long aged beer you shouldn't need any additional yeast!