Mixing natural carbonation bottling and force carbonation can be tricky, because the amount of priming sugar needed varies depending on how much beer you intend to bottle. Software like iBrewMaster (for the iPhone and iPad) can calculate this, as other can as well I'm sure.
If you only intend to bottle 10 bottles, then I'd suggest investing in a counter-pressure bottle filler. I use the one from morebeer --
http://morebeer.com/view_product/18279//Counter_Pressure_Bottle_Filler
My buddy uses the Beer Gun from Blichmann, which he also likes. Theres about 30 bucks of hardware you need in addition to the MoreBeer bottle filler, so it's entirely possible that the Beer Gun is a better investment. Either way, you'll want to have some method of bottling from carbonated kegs if you're going to be doing this for a while.
As for adding yeast as a secondary measure, it's almost never necessary. There's still yeast suspended in your beer, even if it's clear. If you're going to add yeast, just get a pack of dry ale yeast. There's no flavor to impart, as your beer has finished fermenting. Just add a pinch to each bottle and you'll be fine. What doesn't eat up the priming sugar will flocc out. Don't drink it.
As for kegging primed beer -- I have no idea what'll happen as I've never done it. You won't damage your keg, but your beer might be overcarbonated. If you do this, and your keg is in the fridge, you probably won't be done carbonating for about a month. You're better off segregating a quantity to bottle and force carbonating the rest. It'll be drinkable sooner and you won't run the risk of having a foam-a-thon in a glass.