Hello Doc why are you saying lubricate the lock barrel which lock barrel,
All four** of them. That's both front doors, the boot lid and the ignition lock. The good news is that it's quick, cheap and easy to do:
give each barrel several copious squirts of solvent cleaner(brake/carb/contact/whatever you have).
rub a soft, good quality pencil over the sharp bits of the key and
pump it in and out of the barrel a few times.
Finish the job by ensuring that the keyring you use for the ignition holds a
maximum of one key.
While you have the cleaner handy, use it on the both parts of the bonnet latch then grease them both and as much of the inner cable as you can see.
**I know Omegas might not have four, but this isn't Omega specific advice.