I just want to say your paintings are really nice! Personally I only really have experience with a few mediums, but one I have enjoyed using is pure cold pressed linseed oil as my medium (along with odorless mineral spirits if you really need to thin the paint) because it makes it really buttery and smooth, and helps slow drying time. But, I understand you want to speed up the drying time, and unfortunately I have only used Gamblin Galkyd, which I honestly didn’t really love.

Hi Marcus! I wanted to reply because I saw your post has no comments. Regarding your question, I think it's important to determine what it is you want out of the hair, and why you are looking for help with it. Does something about it stand out as problematic to you? Or do you feel it could be more successful, but you're not sure how? Perhaps the very best thing you could do would be to look at examples of hair painted by those you admire, study them, and try to apply some of the things you like to this painting or to your next. Overall, I think your painting is very good! Keep it up.