which bluing solution/black solution for engraved metal?

[swift]

I'll be getting an AK engraved and would like to fill in the engraving so it does not rust. I do not want to go the route of duracoating (at least not yet).

Here are the different solutions I found at Brownell's. Which should I use? Would you recommend something different?

Thanks.

http://www.brownells.com/.aspx/pid=27174/Product/GUN_BLUE___BLACK_KITS

http://www.brownells.com/.aspx/pid=8795/Product/EXPRESS_BLUE__1_EXPRESS_BROWN__2

http://www.brownells.com/.aspx/pid=1085/Product/DICROPAN_T_4_reg_

http://www.brownells.com/.aspx/pid=1109/Product/DICROPAN_T_4_reg__CREME

http://www.brownells.com/.aspx/pid=24776/Product/PERMA_BLUE

[ar15barrels]

Any of the cold blue type solutions will worsen the rust situation, not reduce it.
The only way to eliminate/reduce rust is to keep it oiled.
Parkerizing works so good in this respect because it leaves a rough surface that holds oil.
Painting (duracoat and others) will seal the metal so it won't rust.