there are a few things you can try to get deeper and more even bluing.

the first one is to heat the blade up with a hair dryer. nothing extreme, you just want it warm to the touch. i've been told the pores on the steel will more readily accept the blue.

second one is to really massage that stuff in there, don't just coat it and leave it. i would work it over until the bluing got white and foamy they i would rinse it off with hot water.

and the last one is to hit it with a touch of oil, after my blades are clean i put a light coat of food safe mineral oil on them.

i blued a m4 blade a while back and after using those techniques it came out gorgeous.