Could you tell us the best way (or your way) to disable a live primer? I've heard you could put oil in the casing and let it sit for a few days would do it.

I have one casing I could use if it was disabled.
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Do NOT[/size] rely on oil to deactivate a primer. Modern primers are quite resilient to oil contamination.
The [size=+1]only[/size] safe way to disable a life primer is to fire it in a machine (such as a rifle) designed for that purpose, taking all the same safety precautions you would in firing a live round.
If you have a shellcase with special meaning that has a live primer, send me a PM and I'll arrange to deprime it for you. If it's an ordinary primed shellcase, then just using a different one is cheaper, simpler, and safer.
Regards,
Eric