1. Should climbers be tightening bolts?
YES. The crag's safety is everyone's responsibility. There's no crag fairy that makes sure the bolts are tight. Most climbing organizations won't even come out just to tighten a loose bolt. Multiple climbing organizations recommend carrying a 9/16" wrench with you. https://squamishaccess.ca/hanger-nut
2. Will it fit in my chalk bag?
Your chalk bag will need to have an elastic loop that sticks out like an ear in order for the Crank Brush to fit. Fortunately, that seems to be most chalk bags. Here's a video of me testing the Crank Brush with every chalk bag at Colorado's Flagship REI Store.
As long as you have a stretchy loop that isn’t sewn narrow like on that grey metolius, or I believe, la sportiva black and yellow bags, it should fit.♬ original sound - Crank Climbing Brush
Chalk bag brands that the brush does not seem to fit (not a comprehensive list):
Petzl (Loop is sewn to the side of the bag and not elastic)
Newer Metolius (Loop is sewn to the side of the bag)
If the brush does not fit in your chalk bag, I recommend purchasing an Organic Chalk Bag. They're a great company and their bags are super high quality, plus the Crank Brush fits in the holster snugly.
3. Are all bolts the same size?
All bolts are not the same size. Back in the 80s and early 90s, they used 5/16" bolts. But since then, they have become much more standardized. Most route developers, as well as groups that do crag rebolting efforts such as the Boulder Climbing Coalition and ASCA, use 1/2" sleeve or 3/8" expansion bolts. The Crank Brush has a 9/16" SAE socket that fits on both of these bolt types. As long as you're in the USA or Canada and aren't climbing at an old remote crag, the Crank Brush should work for you.
4. Won't it break?
The Crank Brush is incredibly strong. It's made of the same material as plastic bicycle tire levers. However, it WILL break. It breaks at about 20 ft/lbs of pressure, which on a 5" long brush is most of your body weight applied to the brush. Also, 3/8" expansion bolts are not meant to be tightened above 25 ft/lbs anyway. So think of it as a failsafe. I've used my same Crank Brush for over a year and have tightened dozens of bolts and it's still in great shape.
5. Can I use it to brush my teeth?
Ehhhh? Ask your dentist.