Door locks, trunk locks, ignition lock cylinders....

If you have several donor tumblers, you should not need to be filing anything.

Tip # (what are we on now?)-

Decide what lubricant you will use...and stay with it.

WD-40 or similar is easy and everyone has it but...

"Real" locksmiths use graphite.

Graphite lasts much longer although it used to be somewhat difficult to find and expensive.
It's much easier to find now, but still a bit pricey.

What ever you do, DO NOT mix WD-40 or similar with graphite.
It makes a sticky paste that will gum up the lock which will eventually stop working.