The WDNNSBG works great. You probably have all the materials laying around spare as it is anyhow.
When I keg, I generally do a hybrid carb routine. I'll dose the entire keg with 1/4 to 1/3 cup of corn sugar and let it condition for about a week or so. Then I'll stick it in the keezer and hook the gas line up to it. About two weeks later, it's perfectly carbed and at optimal drinking age. Blow off the first slug of yeast sediment from the bottom and drink away.
Since I'm kegging within 2-3 weeks and it's usually not optimal drinking until 5 or 6 weeks, the extra bit of time is no problem as far as I'm concerned.
If you are in a hurry, though, remember that higher pressure and higher surface contact area increases the absorbtion rate. Using a higher force-carbing pressure cuts the time down, as does shaking or any other method to create bubbles (which increases contact surface area).