If you want to do it quick and easy, you can't beat these:
Used to inject lubricant into cable housing it clamps over the end of the cable and has a port for the thin straws that come with aerosols, quick and clean.
Only around $10, I like the motion pro version because it uses two clamp screws and is a bit longer than similar tools.
Motion Pro Version
The nice thing about these type of oilers is that you can use it with carb or electric spray to wash out all the fine bits of dust that gets inside the cables over the years. I have found that it help quit a bit doing this first. You can also use a rubber tipped air blower to force air into the small hole that will force the debris out when you spray the cleaner through the cable. Then when it's all clean and dry, spray the cable lube in. All of this might take about 5 minutes tops. It has my vote!