I fill bottles the same way some brewpubs fill growlers. Just use a hose attached to the tap. If you happen to have the right size vinyl or silicone hose, it may slide right into or over your faucet. Lowering the pressure on the keg can help reduce foam. Ideally, you want just a very small amount of foam in the bottle so that you can "cap on foam" to eliminate oxygen in the bottles. A beer gun or BMBF is better for larger volume bottle filling, but for a cheap way to fill a few bottles, it works for me. (I've entered beers in competitions with bottles filled with this method and scored in the 40's.)