I think I have to say that I like the Hair Spray the best. It seals the page enough so it does not rub off, adds no brush marks and doesn't make it really glossy. One of the point of using oil pastels is all the instant texture you get. You lose all that when you put a finish on it. It seems that hair spray lets you keep more of your original look. So that is what I will be using from now on.
Here is a fun story I wanted to share. Its about a bird a woman and greeting cards, click on this link to read it. story