After soaking, most brewers I know toss in a wet papertowl (or shop cloth), plug the opening, and swirl the towel around to remove the last of the gunk. This works well for wide-mouth bottles but not so much for narrower glass bottles.
Here's a great inexpensive DIY project created by Casey Weed that cleans even the narrowest of bottles!
Casey describes some of the project below and be sure to hit the link (or the picture above) for the full instructions.
"I recently put together a handheld carboy/keg pressure washer and hadn’t see anything like it so I thought I would share. I always have trouble getting the dried up krausen on the top of the carboy off with my brush and always felt like it would come right off if I could get a little pressure on it. This is what I came up with.
- Racking cane
- 6’ 3/8” vinyl tubing
- 3/4” Slip to 3/4 FHT (PVC) adapter
- 1/2" FPT X 3/4" Slip (PVC)
- 1/2” MPT x 3/8 barbed (vinyl)
- Two small stainless hope clamps (I think 5/16”, I already had these)
- Screw thread protector (sorry, I don’t recall the exact size. Get the tightest you can) Drill a hole in the tip, I used a 1/8” bit."