Quicker... right... <.< Anywho, despite being given free reign to wallie, I think I'll keep this short. I don't want to eat up your time with reading a long post, or my time for making a long post... So yeah, I'll do my best to keep it simple (keep in mind I'm actually writing this first, so it may turn out longer than anticipated).
Basically, there are two types of cells vital to the structure of bones - Osteoblasts and Osteoclasts. The Osteoblasts, simply put, are in charge of mixing proteins and minerals to form bone tissue, and Osteoclasts are, also simply put, in charge of breaking down bone tissue into the proteins and minerals which make up bone. These two cells, which do their jobs in groups, work together to constantly remold the bones within the body - the Osteoclasts breaking down bone tissue so that the Osteoblasts can redistribute it. This makes "bone" a dynamic tissue, as it's in a state of perpetual reformation. However, the bone in a Kaguya's body is... more dynamic.
By using chakra to invoke the process of bone reformation, as well as general calcium generation and manipulation within the body, a Kaguya may control how bones are formed, including where in the body they are made, how they are shaped, and all other properties right down to their density.
Due to these characteristics of the Kekkei Genkai, it's used heavily as a supplement to Taijutsu. By extending bone to pierce through the skin via the method mentioned above, one can form any kind of weapon or tool, at any kind of strength, ranging from regular bone to steel-like strength (including a strength which can't be cut by a Chakra-Infused Blade, which can nearly anything). Aside from from weapons, the bones can also be used as a defense mechanism, either by simply increasing the density of one's bones inside their body so as to increase their strength and turn the user himself into a type of living shield, or to have bones protrude from their body at random angles so as to damage anyone engaging in close-quarters-combat.
The Shikotsumyaku can also be used at range, though this is less common. Kimmimaro was shown firing off his fingertips like bullets, which either shows that he has chakra control to the point where he can use it as a firing mechanism, that Kaguya bones can grow in so fast that they will push out the old bones with bullet-like velocities, or that he simply has such fine control over the bone itself that he can make it move with such speeds without a build-up of chakra or growing bones to fire it - that it can be launched as though it were simply growing out of his skin with that speed. The user can also send bone out of their body (I'm assuming Kimmaro released bone from all over his body as he was underground, but we would probably have to release bone from our feet if we're standing on the ground) and have it grow and spread, making bone grow out of bone in proportions and speed that completely defy the medically logical, even with the ability to control Osteoblasts, Osteoclasts, and general Calcium. In this manner, the user can cover the battlefield with sharp bone "blades" which extend several meters into the air. They can also become one with the bones and move around the interconnected network at high speeds.
Now, did I miss anything? If there's something important you think I glossed over or missed, please tell me. Otherwise, I don't have any questions at this point.
And yes, sad that you can't write wallies now. >_>