I read another post where he said it would bond to stainless if it had been prepped. Alcohol should be ok to use on blued steel, as long as some protection was applied soon afterwards.
I guess my concern would be that it would somehow seal in either moisture or that some part of either opti-coat or the solvent that keeps it in suspension is corrosive to blued steel, causing it to pit or rust.
I realize it would quickly wear away on moving parts, but if it simply kept the outside of the gun looking new it would be awesome!