Note that a cobalt drier such as the one listed above will push the color of the finishing oil awards green (when you add a deep dark blue to a golden yellow) which can be rather alarming at first.
According to Langridge:
"When initially mixed together, the driers will impart a blue/green cast to the oil or medium with which it is mixed. Exposed to indirect sunlight for a few days will remove this colour difference (Exposing the oil or medium to indirect sunlight will not sun bleach or thicken the material). If used in correct proportions, the colour of the cobalt drier will not interfere with oil paint brightness or colour saturation."
I also add a little red oil to develop a rich brown colour to the finishing oil.
Note, also, "Cobalt Driers are known as ‘surface’ siccatives (driers) and will only speed the drying of the surface of the paint film. They are not ‘through-film’ siccatives and do not perform as successfully with thick films of oil." I'd very much like to try colorless Siccatif de Courtrai
https://www.lefrancbourgeois.com/row/product/white-courtrai-siccative/ https://en.pebeo.com/catalogue/siccatif-de-courtrai-75-ml-75-ml-650401 "This zirconium-based siccative acts in depth and on the surface. It accelerates drying and balances thick layers while hardening. It is very powerful and must be controlled with care. Colourless, it does not alter light colours." I can't find this product in the US however.
