I heard of a good top-tip today…
To ease a stiff lock barrel, don’t use oil as this will attract dirt and bind up the lock again. Instead use the graphite from a soft pencil.
Scrape some pencil lead onto the key and put it in the lock a few times….sorted!
I was so impressed with the results I had to share this.
That is why they sell Graphite powder (packaged in a “puffer”) in hardware stores. 
Best Regards,
George
Thanks for sharing. I have used it on winter coat zippers
I often use a graphite stick (also called a “pencil”) to directly deposit the lube where I need it, just rub it on. Put it on the teeth and sides of a key now and then and it will distribute itself as it rubs off inside the lock. Works great and is less messy than powders.
My locksmith told me about “graphite sticks” as something of a joke, offering to sell me one for a dollar to maintain my locks. When I said I’d take one as it seemed cheap enough he handed me a pencil and said “nah, here’s one for free”.
Phil