We've had trouble with a couple of deadbolts getting hard to operate.
I've fixed this by taking the lock apart, and squirting graphite into
the 'slider' mechanism. This works, but the fit is snug, the graphite
seems to have a little difficulty getting to where it needs to be. Plus,
I end up with black powder on everything.

Can I use something more liquid for this - 3-in-1 oil, or silcon spray,
or something?

Thanks,
G