Use alkyd white instead of normal white to mix with your oil paints.
Drying oil painting in the sun.
This process is demonstrated in the painting below.
Use an alkyd medium with your colors.
Since linseed oil dries faster than other kinds of oil mixing a little extra linseed oil with the paint on your palette can help speed the drying time of your painting.
Oil paintings need daylight.
Buy some commercial paint hardener or dryer to dry paint in a hurry.
When i start an oil painting i will usually thin the paint using odorless solvent so that it becomes a thin wash with a watercolor like consistency.
How to make your oil paintings dry quickly.
6 mix your paint with a solvent like turpentine or liquin.
Not direct sunlight due to fading and too much darkness will cause it to yellow.
Stir it periodically to hasten drying.
One leave the painting to dry in a well ventilated open area where air circulates a fan helps.
Add absorbent materials such as sawdust or cat litter to the paint if there is more than just a little left.
Sun thickened linseed oil is a created by exposing the oil to the sun to create a thick syrupy somewhat bleached oil with similar brushing qualities to stand oil.
Two paint using thin layers and washes which will dry reasonably quickly.
Pour paint from a full can into other cans or containers a little in each so it dries quickly.
A couple of other things to think about that.
In general i agree with what has been said so far its not a good idea to leave an oil painting in full sunlight for an extended period of time this will affect certain pigments.
The sun will take away the color.
To speed up the drying time you can turn on a.
To minimize debris getting in but so that the air can flow through.
Pour some oil about an inch into a wide dish cover it with a propped up lid i e.
Also paint is slow to dry in a cold environment so a warm room is preferable.
Bugs will get stuck to it.
This will make your paintings dry in a day or two compared to a week.
I typically find this is not such a good method as the paint dries too.
Avoid extreme heat like hairdryers as this will only make the process worse.
As you may have guessed from the prior answers drying an oil painting in the sun is the wrong thing to do.
After that i embrace the slow drying time of oil paint rather than try to avoid it.