Every installer will have their own method of sealing threaded connections. Some will use pipe dope, some will use Teflon tape, however based on years of experience with professional builders, the product we choose to include with all of our kits is LocTite 545. We understand that many of our brass DOT fittings come pre-coated with a thread sealant from the factory. With that being said, we highly recommend using the Thread Lock even on these fittings. As the saying goes,"...an ounce of prevention is worth a pound of cure..."
When using the Thread Lock, know that only a drop or two per fitting will suffice, because when you thread it, it will spread it. Also, DO NOT put the Thread Lock on the first threads of the fitting. This first revolution will push the Thread Lock liquid into your system. This could cause a blockage in any of your components i.e. gauges, manifolds, valves etc.
Finally, we can't emphasize enough the importance of allowing the Thread Lock to fully cure for AT LEAST 12 HOURS before pressurizing the system. We know boys and their toys and we don't want you to undo all of the work you just did.