If you can get hold of one, you want to use a depth key. Kwikset uses 6 distinct depths and Schlage uses 5 (IIRC), so use the deepest one. You can also probably find the specs on-line, and cut your own. Try on-line sites for depth keys, or go to a locksmith or old-school, mom 'n pop hardware store. Tell them you are re-pinning a lock for a master key, or are an amateur locksmith, but somehow misplaced your depth key set. Ask to copy theirs (you'll end up with around half a dozen keys). Make sure you know the brand of the lock - most Kwiksets have 5, but their "high-security" models have 6 - so you'll need a different set of keys for each type of lock. My house key is a 6-pin KW10 key, while my other KW keys are all 5-pin. If you're not sure, count the number of flat spots or grooves (not ridges) and you'll know the number of pins.
As far as actual technique, I'll start off with this: Some locks are extremely difficult to "bump". They are coming out with newer models that are "bump-proof", and work by absorbing the shock. Generally speaking, Kwikset is the easiest to bump (in my opinion), and fortunately is one of the most common brands out there.
You have to apply *just* the right amount of torsion (aka 'tension') to the lock.... simply put, this just takes practice and experience. Striking the key is more about making a quick snap rather than a hard hit. It helps if your key fits the lock easily (have them run it through the wire brush a few times at the hardware store). If it sticks, it's not going to work.
Personally, I find it easier to just straight-up pick the lock. But that takes practice, too. If you learn to pick locks (pick, not rake), you'll have a better appreciation for the proper amount of torsion to apply. It's really a lot less than you'd think.
Finally, the mandatory legal disclaimer: Bump keys and lock pick sets are usually considered burglary tools. In some cases, it's illegal to have them, period. Other places, it'll just add on jailtime if you get caught in the act. I recommend the "PIP-13" pick set - those 1,200-piece mega spy sets are unnecessary for 99.7% of applications. A japanese set is nice for picking some garage door locks (which are identical to an SC1 key, but made from a thinner blank). Don't waste money on it unless you KNOW you have a use for it.
That was kind of long, and not sure if it was helpful. Let me know if you have other questions, or something specific I can help with...