I'm trying to decide what materials to use to paint or tint black and white photographs made on matt fiber paper. I know that Marshall's Photo Oils are widely used, but I'm worried that they might be too opaque for my purposes. That leaves more translucent materials like water colors, acrylics and aniline dyes. At the moment I'm leaving toward aniline dyes, which are translucent and water soluble. Any suggestions?
I use Prismacolor Premier colored pencils blended with a 1:1 mixture of turpentine and vegetable oil for hand coloring inkjet prints on matte paper. I use both typical inkjet coated paper (Moab Entrada is a favorite) as well as art papers not specifically coated for inkjet printing.
See https://www.photrio.com/forum/threads/hand-colored-inkjet-print.179779/ for a few examples and some more information. I learned about this technique from the book cited in the above post. I have since learned that Marshalls sold (and apparently still does sell) colored pencils for hand coloring in a similar manner.
I have also experimented with Faber-Castell watercolor pencils as well, but I usually use the Prismacolor. I am not sure I can say why!
I have found that colored pencils (of either type) are not great for covering large expanses with light colors, such as such as skies with a light blue. For this, I use a wash of highly dilute watercolor pigment applied with a brush. (Interestingly the blue I use does not show up well in scans, so my on-line examples have lost this subtle effect.)
Watercolor is a bear to try this with, there are no second chances. Any brush stroke that's applied over another brings up the color from the first stroke. Plain old oil paints, Q-tips and tiny brushes will be your friend. Oil is soooo much easier, you just push it around, lift it up if you don't like it, blend it in wet or when it "dries" (oil paints never dry) etc.
I've used the Marshall's oils a fair amount and have never thought them to be too opaque. The key is to use as little as possible. I use Q-tips or makeup applicators (there are some with narrow tips - more narrow than Q-tips) and try to apply in circles and spread it around before it dries. That lets the tones of the print itself show through. Depending on what you want as a look, you're probably going to need to try some experimental ones first and don't try for the masterpiece version first.
I think the best way to do it is to use regular oil paint. Back in the day I did quite a bit of it but then lost interest. Here is one with oil color and one with pencils. Don't remember the pencils I used. Probably watercolor pencils. You will get much bolder color with oils. One thing that helps is sepia toning the photograph first. Colors tend to look better on a sepia toned print.
If you want to use oil paint then you want to use the transparent colors. Pretty much every manufacturer has a chart on their website. Just take a look at it and it is pretty easy to choose colors. Not the cheapest way to go but I think it is the best.
If you are going to use oils some manufacturers have water soluble oil colors which might be more convenient. I used to also use Liquin as a medium to make the process easier. I'd recommend that as well. You will probably want to thin down the paint.