Home tanners as myself do not alway have the luxury of a tumbler and are often left holding a hide that has ess than the desired results. I posted this as a reply in another spot but thought some new tanners maybe could gain from my post.
I have found much of it depends on the tan, methods adhered to, and at what point you start breaking the hide. If it is not a good tan you won't get the results you expected. When you get a good tan you will be surprized how easy it is.
For breaking Hides
I have used this contraption for about 14 years. I can use an edge on one spot or drag the whole beaver or otter across the top. See photos at http://www.geocities.com/lfabich/Tanningref/breaker.htm
Also I have found that working the hide by hand will do a lot. Trying to crush and bend and twist the hide while holding it between two hands. This actually can had a lot of breaking to a hide. Think of the hide as a piece of wax paper. The more you crush and twist the paper the more the paper becomes uniformly white with cracked fibers. This can be very effective on furs such furred animals such as fox, otter and smaller.
I also have a wood lathe that I use as a sander. I have made a 2 inch dowel about two feet long. To this I have contact cemmented a strip of heavey duty 50 grit sand paper. It works quite well on the tanned hide to thin and clean up. I cup the hide under my gloved hand. and use my palm to guide and apply pressure to the hide as I sand it. I have found this to be a lot more controlled than a belt sander. I do have a fleshing machine but I know that new tanners do not. Breaking down can be a frustrating deal at times.