Avoid extreme heat like hairdryers as this will only make the process worse.
Drying oil painting in the sun.
Not direct sunlight due to fading and too much darkness will cause it to yellow.
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.
One leave the painting to dry in a well ventilated open area where air circulates a fan helps.
Also paint is slow to dry in a cold environment so a warm room is preferable.
Pour paint from a full can into other cans or containers a little in each so it dries quickly.
This process is demonstrated in the painting below.
A couple of other things to think about that.
To speed up the drying time you can turn on a.
Use alkyd white instead of normal white to mix with your oil paints.
Combine linseed oil with the paint on your palette.
This will make your paintings dry in a day or two compared to a week.
This layer of paint dries quickly within 24 hours.
Bugs will get stuck to it.
Add absorbent materials such as sawdust or cat litter to the paint if there is more than just a little left.
The sun will take away the color.
Use an alkyd medium with your colors.
However there is an important exception and that is when an old painting is suffering from discoloured or yellowing of the varnish layer.
How to make your oil paintings dry quickly.
Stir it periodically to hasten drying.
Pour some oil about an inch into a wide dish cover it with a propped up lid i e.
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.
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.
Two paint using thin layers and washes which will dry reasonably quickly.
To minimize debris getting in but so that the air can flow through.
Oil paintings need daylight.
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.
I typically find this is not such a good method as the paint dries too.