I use artist grade safflower oil and an alkyd dryer to create my painting medium. It is a combination that allows my painting to stay wet for two to three days (depending on the colors, and thickness of paint used). I put a very thin layer on my canvas before I start to paint (the wet-into-wet method), or it can be used by adding a little to your brush as you paint.
It has no odor. It is oil based, so you should use caution when using any oil based products as they are flammable. Do not use near flames, use in ventilated area. Keep out of reach of children.