Originally Posted by dfariswheel

A major advantage of Dicrophan T4 is unlike most other cold blues it won't start to puddle on the surface after an application or two.

After applying and flushing with hot water, I give it a spray with 91% or denatured alcohol to insure a clean surface, dry with a hair dryer to dry and warm slightly and apply again.
I've put on as many as 8 coats this way.
Years ago I blued a Marlin 39-A trigger this way, and years later the finish is still perfect and unworn after a lot of use.

Another trick is to pour a little T4 in a cap and apply with a small brush.
This prevents contaminating the bottle and seems to give better, non-streak coverage.
Pitch whatever T4 isn't used.