There was a technique of replacing black areas of the print. First,
chemicall
process dilutes unexposed emulsion and lives jelatine on exposed parts.
Secont, strokes of angle-cut brush lives paint on jelatine and lives
white areas
untoched.
Obviously, this process will not work with Ilford Multygrade RC Paper.
If you want
to use it, you will possibly need to make you own paper :-)
The possible name of the technique is Brom-Oil. I don't know Ehglish
name, so it is
only a guess.
This technique was popular in Europe before WW1 as an alternative to
painted portraits.
It is easy to tell it from painted photograph. Retouched photograph's
colors looks a
bit dirty because paint mixes with gray tones of the photograph.
Brom-Oil
allows you to get clear colors not mixed with grey.
Hope that helps
alexj