OK what you do is take a negative and make a Print from it size 9 by 12. After it has dried and you like the print. The next day you bleach the print so nothing is there.
Let it dry and then on the next day you put it in warm water for 10 mins. Remove it and take off the extra water. Now put the bleached print down on a table and take a Oil brush with the color you want to work with and hit the print over and over again till you start see your photo come back. The oil color will only say where the bleached print was before not on the paper its self. It takes about 4 hours of work to get the look you want. You must start out with only a little oil color on you brush. Slowly adding more color as you go along. If you want to lighten up areas you take a dry bursh and hit those areas. There are many website on the subject of Bromoils.
Here are just some of them.
It is not for everyone. It thaks a lot of time to make one Bromoil.

Sir William