Planted Tank Guru
Join Date: Jul 2010
Location: Huntington Beach, CA, USA
Umm! I guess you know this is not a quickie??
The date on the tank might be a question before doing too much. Good hydro test date? Any firm knowledge of whether it is a working reg,etc?
I would start with the tank. Remove the reg and lay the tank down in a pan if you can to soak. It will take some time. Soaking first will make any deposits easier to remove when you get to that stage. Enough water to cover and then lots of vinegar might be a place to start. While soaking overnight or so, use an old brush to swap the exterior of the reg with vinegar. Don't fllod the solenoid electrical parts. Some soaking and some scrubbing will get the brass parts looking much better.
But it may also be true that neither will ever be really pretty again. If there are serious pits in the tank metal, they may not agree to a hydro test.