I learnt that it’s quite a frustrating process to get looking good. You really need bare finished steel and need to clean everything so there is no grease. You also need to get in on quickly and evenly using a clean cloth and rub the liquid in as opposed to just painting on. Wash off shortly after.coming together nicely.
I tried the gun blue on an XT seatpost. First couple of applications didn’t make a huge difference - I think I need to give it a few more coatings.