Can you use oil pastels over soft pastels? If so, how do you think that would look?

In the world of art, as I think you know, there are but two rules and if we stay within the rules we can do whatever our hearts disire. Oils take forever to dry so don't put enything over them, and try it anyways.....whos to say your wrong? They said it to all the greats! Just have fun!!!!