well, basically, get a roll of baleing wire at the hardware store (not electrical wire you want steel), get out your wire clippers and cut it the length of your forearm from elbow to hand - 108 times. Then you can take some electrical tape and bind all the ends together.

These are not only used for training the shins, but for the entire body - it's best with this type of training to follow a classical system, but in general as long as you don't train to vigorously it is safe.

If you train this type of work with too much enthusiasm you can get localized stagnations from hitting too hard - without the adjunctive qigong practices, you will not be moving the energy and this can upset the meridian system causing physical or emotional problems.

If you'd like to look at an example of some traditional methods, check out Mantak Chia's 'Bone Marrow Nei Kung", or Yang Jwing Ming's (I think it's called) the secret of the fountain of youth - on the marrow washing classic of bodhidharma.

Good luck