One of the best drying agents is Liquin by Windsor & Newton. These extend and thin the paint cutting drying time. They will impart slightly different textures to your oil painting, here is a link to a demonstration:https://youtu.be/XEg79XyiXcU
Use thin coats of paint when painting. This a simple way to cut drying time. Although walnut oil paint has a medium drying time compared to linseed oil paint and poppy oil has a slow drying time, my preference is still walnut oil.
Sunlight speeds drying time and is free. Do not use a blow drier, you don't want dust particles in your painting.
You can also thin paint with mineral spirits or turpentine. This will speed drying time because you are thinning the paint. Go to oil paint manufacturers' websites and review their videos.