Just add a few drops to the dry paints, mix them, and give them time to recover. Linseed Oil: adding a small amount of linseed oil can revive dried paints. However, be careful and add the oil gradually to avoid making the paint too liquid.
Unfortunately there isn't any way to reconstitute dry oil paint. Watercolor, yes, oils, no. This is because the drying of oils is actually not strictly a ``drying'' process that can be reversed. It is a chemical change (oxidation) of the linseed oil that the paint was made with.
Like traditional oils, water soluble oil paintings cannot be reactivated with water when dry. New water-mixable mediums have been developed for water mixable oils: quick dry mediums (my favorite), stand oils, painting mediums and impasto mediums, linseed oils and alkyd mediums.
About the only thing the rain would do to your oil base primer is slow down the cure time and maybe hurt it's appearance (water spots and uneven sheen) nothing to worry about. Give it a light sanding when dry and apply your finish paint.
Water Damaged Oil Paintings are a common problem
Typically, the paint will bubble, blister and flake. There may also be a covering of fine white powder or mould around the affected area.
Use thinning agents: linseed oil or turpentine can be helpful. Just a few drops added to the tube will restore the paint's consistency. Heat treatment: if the oil paint has become too thick, you can use heat treatment. Warm the tube briefly in warm water or wrap it in a hot towel.
Oil paint is water-resistant, while acrylic paint is waterproof when dry. You can even clean an acrylic painting with a damp cloth. That said, moisture isn't half so much a threat to the paint itself as it is to the wood stretcher bars, fibers of the canvas, or paper surface the painting is created on.
Highly dilute the paint with spirits of turpentine or white spirit, to decrease the proportion of oil in it and make it more fluid. Wait for the layer to be thoroughly dry before applying the next one.
How to get an oil-based paint to dry. After taking care to protect any unpainted surfaces, spray some white spirit onto any parts that don't seem to be drying. The white spirit should provide the oil-based paint with the solvent it requires to dry.
Lay Multiple Layers: This technique helps reduce the translucent, watery look by adding depth and thickness to the paint layer. Add Dry Mediums: Improve your paint's texture by adding dry mediums like sand, marble dust, or pastes.
Repainting over an old dried oil painting involves first cleaning the surface thoroughly to remove dust and dirt. If the painting is cracked, you may need to apply a layer of gesso to create a smooth surface. Use a light hand when applying new paint, and allow proper drying time between layers.
Oil based paints have a shelf life of anywhere from 2 to 15 years. Depending how well it was sealed and stored. One of the best ways to tell if your stored paint has gone bad is to test it on a piece of board or timber. If lumping occurs it could be that chunky sized bits of paint have formed despite a vigorous stir.
cover your palette in plastic wrap and store in the freezer (must be at -20°C for the linseed oil to freeze) transfer your paints in an air-tight container. use a glass palette instead of a plastic or wooden one (moisture will stay in the paints on a glass surface longer than plastic or wood)
Oil paints dry because of oxidation reactions the evaporation of water caused by the heat of the hairdryer will not speed up the drying time and may even cause your painting to crack. Increasing the temperature may slightly speed up the oxidation reaction but it would not be enough to impact the drying time.
The biggest difference between oil paints and acrylics is that they need to be diluted with solvents. Because oil and water don't mix, after all, adding water to your oils won't make them thinner in the way it does with acrylic paints.
Make dried paints liquid again with water
As acrylic paints are water-based, you can make these paints liquid again by adding water. Hot water is best for this, which you pour drop by drop into the pot. Then stir the dried paint thoroughly and wait for the water and dried acrylic paint to mix thoroughly.
Oil paint: Oil paint is thicker than latex paint and takes longer to dry. Your exterior oil paint will need at least 24 hours to dry completely before getting rained on. If we see a chance of rain in the forecast, we likely won't risk painting your home with oil paint that day.