Yes, you can bottle beers from a keg and hang onto them for a while. My experience is that using a bottle filler is better that pouring out of the tap. I have both the Blichman Beer Gun and a Counter Pressure Bottle Filler from More Beer. I like the counter pressure filler better as it does a better job keeping the head from overflowing the bottle. The Beer Gun is a little easier to use as it is just a trigger pull to both purge and fill. A few tricks I've discovered are, 1) keep everything COLD. Your beer should be very cold, the filler should be cold, and the bottles should be cold. I put the filler and the bottles in the freezer for an hour or so before I start. 2) vent the keg and turn the CO2 pressure down to 2-4 psi. That's enough to move the beer, but keeps it from being turbulent. 3) cap to foam - even if the means just placing the cap on the bottle as soon as it's filled. 4) use oxygen absorbing caps. They will help reduce the chance that your beer will be ruined by oxygen uptake.
If you can get some help capping, that's even better. I generally only bottle to take some with me somewhere, but I did fill 6 cases of various beers this way for a wedding and they came out great after sitting a couple of months.
Best of Luck!
