Looking for comparisons of cold-blue solutions to remove scratches on Parkerize steel (not SS)

Dicropan T4 from Brownells

Brownells link

Rattle can is very sexy.

Brownell's Dicrophan T4 is possibly the best cold blue for this purpose because not only is it more durable then most, it gives a really black color, not the usual blue.
The black color blends in with parkerizing better.

Use a good solvent like Acetone that leaves no residue, then spray dripping wet with 90% alcohol.
Dry with a hair dryer to warm the metal then apply.
Don't over-heat, it's not needed and tends not to work as well as hair dryer-warm.

Great.  I have tried G96 paste.  Seemed to work okay.  Oxy-blue not so good.

Oxpho Blue seems to be very steel dependent.  Soft steel takes it, but harder steel doesn't.  I don't like the product.

How much darker is dicrophan T-4 compared to oxpho blueing?