i use it quite alot. i just used it to blue the hammer on my NMBH flat top .
i smeared it on with a Q-tip , very heavily and waited until it turned black.
i soak a small cloth with gun oil and wipe off the excess .
it came out real nice.
i only use it for small parts. i have never used it for anything big, thats what oxpho blue is for , IMO