I know some love them, some hate them, some say you don't have to get every bit of carbon off your boat tail, etc. What can I say, I still feel like my DI could pop up at any moment. (Sneaky lil' bastard )
So, for those that use the B.O.N.E. or the Cat or whatever tell us what you like and don't like and what tools you'd recommend.

I used the BONE with my Apf Armory bolt. Did I need it? Nah. Never gave me problems, I just got it because it was a good deal and why not? It did pull a little carbon, but honestly if I hadn't gotten it for something like 30% off or more I wouldn't bother. Back of the blade on a Boker Subcom-F did plenty well enough, just took a bit longer.

Recently swapped to an AP bolt, so we'll see how that goes. Tolerances or finishes or something may yield a different result and make the BONE magically worth it.

I'll keep using it since I got it. But I wouldn't buy another one, and probably would recommend it either.

I've tried all the tools mentioned. The BONE, the CAT M4, etc. While they work to a degree, they leave too much behind for my liking.

Nothing beats the old fashion pick and brush. I use the Otis kit and simply assemble the pick to clean out the chamber star, bolt carrier group (the front and back area where the fire pin goes in), and the tail and between spaces of the bolt. I then use the lock lug scarpper to move around a patch to pick up everything. You can just buy the accessory kit here: http://www.otistec.com/pc_product_detail.asp?key=60CD670731CC43B58814515FBACA00C1

I do know in the army what they would do is take a cleaning rod patch holder and use the screws on that to scrape the tail of the bolt and the inside of the carrier. It works very well.

Comes out nice and clean, not a single area of carbon anywhere. You can use the otis kit anywhere else too such as the rail slides of a handgun. The brush is nice to spread oil/grease to the rails of your bolt/carrier.

I use a brass casing or a pocket pen knife.

Kroil and a piece of Scotchbrite pad works pretty good too.

I have a pretty long brass scraper tool I purchased from either Brownells's or Midway USA, I forgot which site. It works very well.  FYI I have no connection to the aforementioned companies I merely use some of their kit.

A piece of .308 or .30-06 brass is all you need if you want to clean off the carbon. 

I like the CAT 4 tool and Slip 2000 Carbon Killer to finish all removal.

A number of people I've talked to were not satisfied with the BONE tool.

Unless you want a tool to take with you, or can't afford the cost, Brownell's sell a couple of very effective tools with screwdriver type handles.
These do a perfect job but are aimed more at a professional gunsmith who does AR work.

I spent the $ on the CAT M4.  I used it 1 time & said to my self this is slow & pointless.  Never used it again.

I like the bone tool. It does a decent job. Nothing is perfect, but I have no complaints . Wardawg

I use the G&G one and am pretty happy. Has  metal scraper and also can clamp tail around a piece of scotchbrite (comes with several scotchbrite pads cut to size). S mple and seems to work well.

I have the CAT tool. I like it. Cleans the Bolt tail very easily.

Bone tool here.  Works pretty good for me.  I don't let them get very dirty between cleanings though.

Whatever tool you use, first apply a good carbon cleaner, let soak for 15 minutes, brush with hard nylon bristle brush, and wipe with cloth.  Repeat, allowing an hour soak this time.  You'll find less to scrape away is left behind.  You may want to try a few different carbon cleaners.

I use my $60 fleabay ultrasonic and it works very well, saving time and effort.  Put part in plastic dish with cleaner, which you can save and reuse.  Place dish in water in ultrasonic.  Try brushing a bit between runs. Always run ultrasonic for 5 minutes first, to eliminate air, then add part.  Warming helps as well.

What do you do with the brass casing?

Please. I'd like to hear more. How is this done?

Thanks.

If you feel the need to scrape (personal preference thing), an empty brass case works very well as is and some folks flatten the bullet end and use as a scraper. Simple and free.

Go to about the 22 minute mark and see how he cleans / scrapes with a .223 / 5.56 empty case. The profile of the case neck makes it an ideal cleaner. Good guy and good video for those new to cleaning ARs. https://www.youtube.com/watch?v=ZMuWlomfnf4

Thanks. I appreciate it.